chore(parser): update readme

packages/bbob-parser/README.md

@@ -5,8 +5,16 @@
 
 Valid for use with [posthtml-render](https://github.com/posthtml/posthtml-render)
 
+## Install
+
+```bash
+npm i @bbob/parser
+```
+
 ## Usage
 
+### API
+
 ```js
 import parse from '@bbob/parser'
 
@@ -17,7 +25,7 @@ const options = {
 const ast = parse('[url=https://github.com]hello world![/url]', options)
 ```
 
-## Results 
+**Results to** 
 
 ```json
 [
@@ -30,3 +38,17 @@ const ast = parse('[url=https://github.com]hello world![/url]', options)
     }
 ]
 ```
+
+### PostHTML
+
+```js
+import render from 'posthtml-render'
+import parse from '@bbob/parser'
+
+const options = {
+    onlyAllowTags: ['url', 'h'],
+    onError: (err) => console.warn(err.message, err.lineNumber, err.columnNumber)
+}
+const ast = parse('[url=https://github.com]hello world![/url]', options)
+const html = render(ast) // <url url="https://github.com">hello world!</url>
+```