feat: luarocks/rocks.nvim support

Hey :wave: ### Summary This PR is part of a push to get neovim plugins on [LuaRocks](https://luarocks.org/labels/neovim). See also: - [rocks.nvim](https://github.com/nvim-neorocks/rocks.nvim), a new luarocks-based plugin manager. - [this blog post](https://mrcjkb.github.io/posts/2023-01-10-luarocks-tag-release.html). ### Things done: - Add a workflow that publishes tags to luarocks.org when a tag or release is pushed. ### Notes: > [!IMPORTANT] > > - **For the luarocks workflow to work, someone with a luarocks.org account will have to add their [API key](https://luarocks.org/settings/api-keys) to this repo's [GitHub actions secrets](https://docs.github.com/en/actions/security-guides/encrypted-secrets#creating-encrypted-secrets-for-a-repository)**. - Tagged releases are installed locally and then published to luarocks.org. - If you push tags from a local checkout, the workflow is triggered automatically. - If you use GitHub releases to create tags, you may need to [add a PA token](https://github.com/nvim-neorocks/sample-luarocks-plugin?tab=readme-ov-file#generating-a-pat-personal-access-token) for the workflow to be triggered automatically. - Due to a shortcoming in LuaRocks (https://github.com/luarocks/luarocks-site/issues/188), the `neovim` and/or `vim` labels have to be added to the LuaRocks package manually (after the first upload), for this plugin to show up in https://luarocks.org/labels/neovim or https://luarocks.org/labels/vim, respectively. See also [this guide](https://github.com/vhyrro/sample-luarocks-plugin).