Neovim provides `stdpath` to abstract the directory paths that it uses based on the OS. It respects `XDG` specification on Linux and uses `%LOCALAPPDATA%` on Windows.
1. Use `stdpath('data') . '/plugged'` for plugin directory.
2. Use `stdpath('config')` for user-config directory. This is `~/.config/nvim/` on Linux and `%LOCALAPPDATA%\nvim\` on Windows.
