chore: add readme

Author: aminya

README.md

@@ -0,0 +1,73 @@
+# terser-config-atomic
+
+The Terser configuration used in atom-community.
+
+## Installation
+
+```
+npm install --save-dev terser-config-atomic
+```
+
+<details>
+<summary>This package also needs `Terser`.</summary>
+
+Either add the following to your `.npmrc` if using `pnpm` to hoist the Terser bundled with the config
+
+```
+public-hoist-pattern[]=*
+```
+
+Or install `terser` yourself in your `devDependencies`.
+
+If using `npm`, the terser dependency is hoisted automatically.
+
+If you use `Parcel` or `rullup-plugin-atomic`, `Terser` is already included.
+
+</details>
+
+## Usage
+
+Create a `.terserrc.js` with the following content
+
+.terserrc.js
+
+```js
+module.exports = require("terser-config-atomic")
+```
+
+The config is adapted based on `NODE_ENV`, so make sure to run your scripts with the correct `NODE_ENV`:
+
+- test: `cross-env NODE_ENV=test your_test_script`
+- development: `cross-env NODE_ENV=development your_dev_script`
+- production: `cross-env NODE_ENV=production your_prod_script`
+
+**Node**: [`cross-env`](https://www.npmjs.com/package/cross-env) is an npm package that you need to install.
+
+## Modifying the config
+
+To change the config use the following pattern:
+
+.terserrc.js
+
+```js
+const TerserAtomic = require("terser-config-atomic")
+
+module.exports = {
+  ...TerserAtomic,
+  // your config here
+}
+```
+
+To change the deep properties such as `compress`, use the following pattern as an example:
+
+```js
+const TerserAtomic = require("terser-config-atomic")
+
+module.exports = {
+  ...TerserAtomic,
+  compress: {
+    ...TerserAtomic.compress,
+    ecma: 2020,
+  },
+}
+```