Support Markdown

[Loki-Astari]

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.