[Docs] Quickstart Guides

[kylechui]

I would like some help from previous users of vim-surround/vim-sandwich/mini.surround, to help me write documentation here. Ideally there should be a sample config to let people get started with nvim-surround by simply copy-pasting into the setup function, as well as some notes about the various differences/quirks in behavior between the plugins.

Everything should be written for the v1.0.0 release and beyond, now that the new API is more stable/fleshed out. Please use the existing vim-surround section as reference, but that is also outdated and should be re-written. Thanks!