Use Neovim’s native plugin/ directory for custom plugin configuration?

[TyceHerrman]

Follow up from #2151 (comment) on using Neovim’s native plugin/ directory instead of the directory-scanning loader in lua/custom/plugins/init.lua

In native plugin/ directory world, folks could put vim.pack.add() and setup code in files such as plugin/git.lua, which Neovim would source automatically during startup.

This would remove the custom loader and be more in line with Neovim lua/ for modules loaded with require(), plugin/ for automatically sourced startup scripts, and after/plugin/ for configuration that intentionally runs later.