Update readme

Author: yuanchuan

README.md

@@ -2,3 +2,52 @@
 
 ![Build Status](https://github.com/css-doodle/postcss-doodle/actions/workflows/ci.yml/badge.svg)
 ![license](https://img.shields.io/github/license/mashape/apistatus.svg)
+
+
+[PostCSS] plugin to use generators from [css-doodle] with the same syntax.
+
+[PostCSS]: https://github.com/postcss/postcss
+[css-doodle]: https://github.com/css-doodle
+[@shape]: https://yuanchuan.dev/polygon-shapes
+[@svg]: https://yuanchuan.dev/experimenting-a-new-syntax-to-write-svg
+
+
+## Installation
+
+```bash
+npm i -D postcss-doodle
+```
+
+## Usage
+
+```js
+postcss([ require('postcss-doodle') ])
+```
+
+
+## Supported functions
+
+### [@svg]
+
+```css
+background: @svg(
+  viewBox: -5 -5 10 10;
+  circle {
+    r: 5;
+    fill: deeppink;
+  }
+)
+```
+
+### [@shape]
+
+```css
+clip-path: @shape(
+  points: 5;
+  turn: 2;
+)
+```
+
+## TODO
+
+* @doodle