docs: add setup

packages/core/README.md

@@ -3,10 +3,84 @@
 [![npm](https://img.shields.io/npm/v/dumble?style=flat-square)](https://www.npmjs.com/package/dumble)
 [![GitHub](https://img.shields.io/github/license/shigma/dumble?style=flat-square)](https://github.com/shigma/dumble/blob/master/LICENSE)
 
-Zero-configuration bundler with TypeScript and esbuild.
+Dumble is a zero-configuration bundler for your TypeScript project.
 
-## Install
+It automatically reads `tsconfig.json` and `package.json` to determine what files to bundle, which is the desired format, where to output the files, and more.
+
+Use [esbuild](https://esbuild.github.io/) under the hood.
+
+## Quick Setup
+
+1. Install:
 
 ```sh
 npm install --save-dev dumble
 ```
+
+2. Add a `build` script:
+
+```json
+{
+    "scripts": {
+        "build": "tsc -b && dumble"
+    }
+}
+```
+
+3. Start building:
+
+```sh
+npm run build
+```
+
+## Configuration
+
+For most scenarios, you don't need to configure anything. Below are some properties you can set in `tsconfig.json` and `package.json` to customize the build process.
+
+```json
+// tsconfig.json
+{
+    "compilerOptions": {
+        // the input and output directories
+        "rootDir": "src",
+        "outDir": "lib",
+
+        // if you want declaration files
+        "declaration": true,
+        "emitDeclarationOnly": true,
+
+        // otherwise
+        "noEmit": true,
+    },
+}
+```
+
+```json
+// package.json
+{
+    "name": "my-package",
+
+    // Set "module" or "commonjs" (https://nodejs.org/api/packages.html#type)
+    "type": "module",
+
+    // Define the output files
+    "main": "./dist/index.cjs",
+    "module": "./dist/index.mjs",
+    "types": "./dist/index.d.cts",
+
+    // Define output files for Node.js export maps (https://nodejs.org/api/packages.html#exports)
+    "exports": {
+        "require": {
+            "types": "./dist/index.d.cts",
+            "default": "./dist/index.cjs"
+        },
+        "import": {
+            "types": "./dist/index.d.mts",
+            "default": "./dist/index.mjs"
+        }
+    },
+
+    // bin files will be compiled to be executable with the Node.js hashbang
+    "bin": "./dist/cli.js",
+}
+```