Support Markdown

Doing "grammar_correction" command removes the markdown on a selected piece of text.

Example:

```
The simplest web application I can build is a web server. A web server maintains no state between calls, and the interface is straightforward. The client sends an [HTTP message](https://developer.mozilla.org/en-US/docs/Web/HTTP/Messages#http_requests) and, in return, receives an [HTTP response](https://developer.mozilla.org/en-US/docs/Web/HTTP/Messages#http_responses).
```

Generates
```
The simplest web application I can build is a web server. A web server does not maintain any state between calls, and the interface is straightforward. The client sends an HTTP message and, in return, receives an HTTP response.
```

Would be nice to maintain the markdown links.

Start by locating the grammar_correction command in the Neovim plugin and reproduce the issue with the linked Markdown example. Trace how selected text is processed, then verify that Markdown links remain intact while the surrounding prose is corrected.

Written by the indexing model from the issue text.