Added some docs on plugins.

[Miro-Andrin]

Started on docs for plugins with help from @Tracreed .

[tim-kt]

What is <path to quill>? Do I need to build cargo-quill first?

[Miro-Andrin]

Yes, If i change it to cargo-quill, does that spark joy?

[tim-kt]

I'm just not sure why you're using a placeholder. You could say "In the root directory of feather, run the following command" followed by cargo install --path quill/cargo_quill/ or you could also say "Navigate into quill/cargo_quill and run the following command", followed by cargo install --path ..

[tim-kt]

I've submitted some wording changes, nothing too major. What's missing for me as an outsider is what the plugin should look like after I create it with cargo-quill (to see if I made a mistake or not) and what the general structure of a plugin is (Plugin trait, implementing this trait, systems, etc).

[Miro-Andrin]

Agree, but we ran out of energy before we got that far.