fix!: move rename `catppuccin` colorscheme to `catppuccin-nvim` (#977)

* fix!: move rename `catppuccin` colorscheme to `catppuccin-nvim`

new builtin colorscheme name conflicts with the plugin name.
adding `-nvim` prefix to indicate the nvim port.

https://github.com/neovim/neovim/commit/d4360596b5ce0d98ab8d81d1fee3e4950cbc4189

* doc: use new colorscheme name

* docs: auto generate vimdoc