add more to the readme

README.md

@@ -1,5 +1,40 @@
 # remark-agda
 
+This is a plugin that processes Literate Agda files that are written in Markdown,
+and replaces it with the HTML directly. This is useful for blogs where you want
+to do additional processing with remark, such as Katex or others.
+
+- [remark](https://github.com/remarkjs/remark)
+- [literate Agda](https://agda.readthedocs.io/en/latest/tools/literate-programming.html#literate-markdown-and-typst)
+
+This plugin has been extracted from the source code of [my blog](https://mzhang.io).
+
+## Installation
+
+```
+npm i remark-agda
+pnpm add remark-agda
+bun add remark-agda
+```
+
+## Usage
+
+```js
+const vfile = await read("/path/to/file.lagda.md");
+await unified()
+    .use(remarkParse)
+    .use(remarkAgda, options)
+    .use(remarkRehype, { allowDangerousHtml: true })
+    .use(rehypeRaw)
+    .use(rehypeStringify)
+    .process(vfile);
+```
+
+Note:
+
+- Since this returns raw HTML, we need the `allowDangerousHtml: true` flag to `remarkRehype`
+  _as well as_ the `rehypeRaw` plugin to convert back.
+
 ## Contact
 
 Author: Michael Zhang