Add instances for URI from network-uri

[phadej]

:+1: / :-1:, @bergmark ?

[bergmark]

Looks like this adds network-uri+parsec+th-compat to our dependencies?

My gut reaction is always no to more dependecies, haha, but I'm also in favor of batteries included so I don't mind either way. Really wish there was a better solution for this on the package level!

[phadej]

Hmm. parsec is unfortunate, but it's bundled with GHC. th-compat is a compat module, which I wouldn't be afraid to depend upon (I'd rather promote that people use it over reimplementing the compat stuff themselves). So this would add "only" network-uri dependency.

[erinclemmer]

I created a PR to add a Read instance for the URI data type. This would make it easier to create a URI constructor for the Value data type.