Flesh out docs/examples in docs directory

[f-f]

I tripped up while following the example usage in README, and noticed that the linked telegram-bot repo might be outdated wrt the latest version of this lib - most notably, since readJSON returns a nice Either, the example usage should contain it explicitly instead of IO and F.

I'll give a try to put together a "beginner-friendly" example section PR.

[justinwoo]

Would be good to have examples from my various posts copied into test/ or examples/ probably.

[justinwoo]

This issue is now converted to being about making sure all of the relevant examples and write up go into the docs/ directory as built by readthedocs: https://purescript-simple-json.readthedocs.io/en/latest/

[justinwoo]

We should actually define some concrete goals in this issue and maybe make a "Milestone"

[justinwoo]

https://github.com/justinwoo/purescript-simple-json/milestone/1

[justinwoo]

Basically done