doc/neovim: explain what buildNeovimPlugin does

doc/languages-frameworks/neovim.section.md

@@ -99,7 +99,22 @@ patch those plugins but expose the necessary configuration under
 `PLUGIN.passthru.initLua` for neovim plugins. For instance, the `unicode-vim` plugin
 needs the path towards a unicode database so we expose the following snippet `vim.g.Unicode_data_directory="${self.unicode-vim}/autoload/unicode"` under `vimPlugins.unicode-vim.passthru.initLua`.
 
-### {#neovim-luarocks-based-plugins}
+#### {#neovim-luarocks-based-plugins}
+
+In order to automatically handle plugin dependencies, several neovim plugins
+upload their package to [](www.luarocks.org). This means less work for nixpkgs maintainers in the long term as dependencies get updated automatically.
+This means several neovim plugins are first packaged as nixpkgs [lua
+packages](#packaging-a-library-on-luarocks), and converted via `buildNeovimPlugin` in
+a vim plugin. This conversion is necessary because neovim expects lua folders to be
+top-level while luarocks installs them in varous subfolders by default.
+
+For instance:
+```nix
+rtp-nvim = neovimUtils.buildNeovimPlugin {
+    luaAttr = luaPackages.rtp-nvim;
+};
+```
+To update these packages, you should use the lua updater rather than vim's.
 
 #### Treesitter {#neovim-plugin-treesitter}