add readme

README.md

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+[![NuGet](https://img.shields.io/nuget/v/ConstructorGenerator.svg)](https://www.nuget.org/packages/ConstructorGenerator/)
+[![GitHub license](https://img.shields.io/badge/license-MIT-blue.svg)](https://raw.githubusercontent.com/k94ll13nn3/AutoConstructor/main/LICENSE)
+![main_workflow](https://github.com/Swarley97/ConstructorGenerator/actions/workflows/main.yml/badge.svg)
+
 # ConstructorGenerator
+
+ConstructorGenerator is a C# source generator which generates constructors for you.
+
+## Installation
+
+Install the [ConstructorGenerator NuGet package](https://www.nuget.org/packages/ConstructorGenerator/).
+
+### Package Manager Console
+
+```powershell
+Install-Package ConstructorGenerator
+```
+
+### .NET CLI
+
+```bash
+dotnet add package ConstructorGenerator
+```
+
+## Getting started
+
+### Prerequisites
+
+ConstructorGenerator requires C# 9.0 or later.
+
+### Usage
+
+Add the `[GenerateFullConstructor]` attribute to your class or struct and a constructor will be generated.
+
+```csharp
+[GenerateFullConstructor]
+public partial class MyClass
+{
+    private readonly ILogger _logger;
+    private readonly IDependencyA _dependency;
+    private readonly IDependencyB _dependencyB;
+}
+```
+
+The generated constructor will look like this:
+
+```csharp
+public MyClass(ILogger logger, IDependencyA dependency, IDependencyB dependencyB)
+{
+    _logger = logger;
+    _dependency = dependency;
+    _dependencyB = dependencyB;
+}
+```
+### Rules
+
+Only for the following members a constructor parameter will be generated
+- Read only fields with no initializer
+- Get only Properties or init only properties with no initializer 
+- Properties or fields with the `[ConstructorDependency]` attribute (this override the rules above)
+
+**Examples**
+```csharp
+// ignored
+private readonly IDependency _dependency = new Dependency();
+```
+```csharp
+// not-ignored
+private readonly IDependency _dependency;
+```
+```csharp
+// not-ignored
+[ConstructorDependency]
+private readonly IDependency _dependency = new Dependency();
+```
+
+```csharp
+// ignored
+private readonly IDependency _dependency { get; } = new Dependency();
+```
+```csharp
+// ignored
+private readonly IDependency _dependency { get; set; }
+```
+```csharp
+// not-ignored
+private readonly IDependency _dependency { get; init; }
+```
+```csharp
+// not-ignored
+[ConstructorDependency]
+private readonly IDependency _dependency { get; set; }
+```
+
+### Ignoring properties and fields
+
+You can ignore properties and fields by adding the `[ExcludeConstructorDependency]` attribute to them.
+
+```csharp
+[GenerateFullConstructor]
+public partial class MyClass
+{
+    private readonly ILogger _logger;
+    private readonly IDependencyA _dependency;
+
+    [ExcludeConstructorDependency]
+    private readonly IDependencyB _dependencyB;
+}
+```
+
+The generated constructor will look like this:
+
+```csharp
+public MyClass(ILogger logger, IDependencyA dependency)
+{
+    _logger = logger;
+    _dependency = dependency;
+}
+```
+
+### Explicitly specifying properties and fields
+
+You can explicitly specify the properties and fields which should be included in the generated constructor by adding the `[ConstructorDependency]` attribute to them.
+This can be useful for the following cases: 
+- If you do not want to use the `[GenerateFullConstructor]` attribute on the class or struct
+- If you want to add additional constructor dependencies which are not included by default (see [Rules](#rules)) 
+- If you want to specify it as optional parameter (see [Optional parameters](#optional-parameters))
+
+```csharp
+public partial class MyClass
+{
+    [ConstructorDependency]
+    private readonly ILogger _logger = new NullLogger();
+
+    [ConstructorDependency]
+    private readonly IDependencyA _dependency;
+
+    private readonly IDependencyB _dependencyB;
+}
+```
+
+The generated constructor will look like this:
+
+```csharp
+public MyClass(ILogger logger, IDependencyA dependency)
+{
+    _logger = logger;
+    _dependency = dependency;
+}
+```
+
+### Inheritance
+
+ConstructorGenerator supports inheritance. You can put the `[GenerateFullConstructor]` attribute on a derived class.
+
+```csharp
+
+[GenerateFullConstructor]
+public MyClass(ILogger logger, IDependencyA dependency, IDependencyB dependencyB)
+{
+    _logger = logger;
+    _dependency = dependency;
+    _dependencyB = dependencyB;
+}
+
+[GenerateFullConstructor]
+public partial class MyDerivedClass : MyClass
+{
+    public IDependencyC DependencyC { get; }
+}
+```
+
+The generated constructor will look like this:
+
+```csharp
+public MyDerivedClass(ILogger logger, IDependencyA dependency, IDependencyB dependencyB, IDependencyC dependencyC)
+    : base(logger, dependency, dependencyB)
+{
+    DependencyC = dependencyC;
+}
+```
+
+Or, if you just want to generate the base constructor call (for example because your derived class have no constructor dependencies), 
+you can put the `[GenerateBaseConstructorCall]` attribute on the derived class.
+
+```csharp
+
+// constructor of MyClass
+public MyClass(ILogger logger, IDependencyA dependency, IDependencyB dependencyB)
+{
+    _logger = logger;
+    _dependency = dependency;
+    _dependencyB = dependencyB;
+}
+
+[GenerateBaseConstructorCall]
+public partial class MyDerivedClass : MyClass
+{
+
+}
+```
+
+The generated constructor will look like this:
+
+```csharp
+public MyDerivedClass(ILogger logger, IDependencyA dependency, IDependencyB dependencyB)
+    : base(logger, dependency, dependencyB)
+{
+}
+```
+
+> **Note**: It doesn't matter whether the base class constructor is also generated by the ConstructorGenerator or manually defined in the code. In either case, the constructor call will be generated.
+
+### Optional parameters
+
+```csharp
+[GenerateFullConstructor]
+public partial class MyClass
+{
+    private readonly ILogger _logger;
+    private readonly IDependencyA _dependency;
+    [ConstructorDependency(IsOptional = true)]
+    private readonly IDependencyB _dependencyB;
+}
+```
+
+The generated constructor will look like this:
+
+```csharp
+public MyClass(ILogger logger, IDependencyA dependency, IDependencyB dependencyB = null)
+{
+    _logger = logger;
+    _dependency = dependency;
+    _dependencyB = dependencyB;
+}
+```
+
+### Constructor accessibility
+
+ConstructorGenerator supports specifying the accessibility of the generated constructor. You can put the `[ConstructorAccessibility]` attribute on a class or struct and the constructor will be generated with the specified accessibility.
+
+```csharp
+[GenerateFullConstructor]
+[ConstructorAccessibility(Accessibility.Internal)]
+public partial class MyClass
+{
+    private readonly ILogger _logger;
+    private readonly IDependencyA _dependency;
+    private readonly IDependencyB _dependencyB;
+}
+```
+
+The generated constructor will look like this:
+
+```csharp
+
+internal MyClass(ILogger logger, IDependencyA dependency, IDependencyB dependencyB)
+{
+    _logger = logger;
+    _dependency = dependency;
+    _dependencyB = dependencyB;
+}
+```
+
+## License
+
+ConstructorGenerator is licensed under the [MIT license](LICENSE).