feat: workflow for publishing to luarocks

[mrcjkb]

Summary

This PR is part of a push to get Neovim plugins on LuaRocks.

• See this blog post, which follows up on a series of posts by @teto.

Things done:

• Add a workflow that publishes tags to LuaRocks.
• Add a LuaRocks badge to the readme (assuming the existence of a lewis6991/impatient.nvim package).

Notes

• For the release workflow to work, someone with a Luarocks account will have to add their API key to this repo's GitHub actions secrets.
• Due to a shortcoming in LuaRocks (https://github.com/luarocks/luarocks-site/issues/188), the neovim label has to be added manually, for this plugin to show up in https://luarocks.org/labels/neovim
• If you would prefer rolling releases without tags, this is also possible.

Adding the API key (screen shot)

[lewis6991]

I should have mentioned sooner, but I am roughly planning to archive this plugin once https://github.com/neovim/neovim/pull/22668 is merged.

I'm still happy to merge this though.

[mrcjkb]

Ah, then I don't think it makes sense to publish this to luarocks.

I'll probably open the same PR for some of your other plugins at a later time :smile: