Problem: The swapmous plugin has to be copied or sourced to be used.
Solution: Turn it into the swapmouse package.
https://github.com/vim/vim/commit/e101204906e10f1e100e2f9017985c61f26b03ac
Justification for changes that do not carry over
- `Filelist` does not exist in neovim
- neovim does not have a `README.txt` in `runtime/macros`
