Implement Zed extension

[alerque]

It looks like WASM is a viable way to create Zed extensions now:

https://zed.dev/blog/zed-decoded-extensions

It's a very code and very little prose focused editor, but this might be easy enough to implement as a plugin for Markdown or other document formats.

[alerque]

Reviewing the current docs on Developing Extensions for Zed it doesn't look like there is any API surface available for directly manipulating text. This would probably have to be implemented as a hack as a Language Server. This may have to wait until they open up a bit more.