We should have a collection with examples of custom surround objects

[mawkler]

I think we should have a collection of custom surrounds to help and inspire people into configuring surround.nvim. I think this would be especially useful to show examples of how to use it together with treesitter.

[kylechui]

These examples should be in #53, but to be honest I've been a bit bogged down by other stuff (internship applications). I'll try to get some more work done on polishing the interface and get v2.0.0 pushed out before working more on the "user-facing" side of things, since I'm still not 100% happy with how things are at the moment. I also would like to better understand how queries work and if that can be utilized in any meaningful way.