Use BuckleScript's native namespacing feature.

[parkerziegler]

This PR adds support for using BuckleScript's native "namespace: true" feature. Rather than all of our module names being Urql* and then renamed in ReasonUrql.re, we just use BuckleScript's native "namespace: true". This is great – our codebase is easier to traverse and module references are more succint. This to address feedback from #170. Would love to get any feedback or opinions from folks before merging. For the most part, the public API doesn't really change. The one piece that does is UrqlTypes is now just Types. So if you do the following:

open ReasonUrql;

and you have a local Types module, you'd get a conflict. Not a huge deal though, because you can make the (wiser) choice to not globally open ReasonUrql and just reference it as needed. If approved, I'll update our code samples to show that pattern a bit more often.

[kitten]

Absolutely amazing work! Must’ve taken a while to rename all of this 😅 I didn’t think it’d work out this smoothly with a couple of renames 🤩🙌

[parkerziegler]

Yeah fortunately there's not too much in repo module referencing – mostly just modules referencing UrqlTypes and needing to get upgraded to Types. But yeah, much smoother than anticipated!