docs: added basic documentation

README.md

@@ -1 +1,104 @@
-# nestjs-google-pubsub
+# NestJS Google Pub/Sub module
+
+[![p-fedyukovich](https://circleci.com/gh/p-fedyukovich/nestjs-google-pubsub.svg?style=svg)](https://circleci.com/gh/p-fedyukovich/nestjs-google-pubsub)
+
+A Google Cloud Pub/Sub library for the [NestJS](https://github.com/nestjs/nest) framework.
+
+## Features
+
+- Pub/Sub configuration via several ways (sync/async/factory/existing)
+- Decorators for injecting clients and topics
+- Support multiple projects
+
+## Installation
+
+**Yarn**
+
+```bash
+yarn add nestjs-google-pubsub-module
+```
+
+**NPM**
+
+```bash
+npm install nestjs-google-pubsub-module
+```
+
+## Usage
+
+Once the installation process is complete, we can import the `GooglePubSubModule` into the root `AppModule`.
+
+```ts
+import { Module } from '@nestjs/common';
+import { GooglePubSubModule } from 'nestjs-google-pubsub-module';
+
+@Module({
+  imports: [
+    GooglePubSubModule.forRoot({
+      projectName: 'gcp-project'
+    }),
+  ],
+})
+export class AppModule {}
+```
+
+The `forRoot()` method supports all the configuration properties exposed by the PubSub constructor. 
+In addition, there is `projectName` configuration property which is used as alias name for a project.
+
+**Important**: Default project name will be used it's not provided.
+
+Once this is done, the PubSub object will be available to inject across the entire project (without needing to import any modules), for example:
+
+```ts
+import { Injectable } from '@nestjs/common';
+import { PubSub } from '@google-cloud/pubsub';
+
+@Injectable()
+export class AppService {
+  constructor(private pubsub: PubSub) {}
+}
+```
+
+### Topics
+
+Once PubSub module is configured, we can set a topic up.
+
+```ts
+import { Module } from '@nestjs/common';
+import { GooglePubSubModule } from 'nestjs-google-pubsub-module';
+
+@Module({
+  imports: [
+    GooglePubSubModule.forRoot({
+      projectName: 'gcp-project'
+    }),
+    GooglePubSubModule.forFeature('event_topic', {
+      projectName: 'gcp-project',
+    }),
+  ],
+})
+export class AppModule {}
+```
+
+The `forFeature` method applies two arguments. The first is a topic name, and the second - option which supports all 
+the configuration properties exposed by Topic publish options.
+In addition, there are extra configuration properties described below.
+
+* `projectName` - name of the project for which topic will be configured (default: `default_project`)
+
+Once this is done, as well as the PubSub object the Topic object will be available to inject across the entire project 
+(without needing to import any modules), for example:
+
+```ts
+import { Injectable } from '@nestjs/common';
+import { InjectTopic } from 'nestjs-google-pubsub-module';
+import { Topic } from '@google-cloud/pubsub';
+
+@Injectable()
+export class AppService {
+  constructor(
+    @InjectTopic('event_topic')
+    private readonly eventTopic: Topic
+  ) {}
+}
+```