Add instances for ShortText

[Boarders]

ShortText is a commonly used alternative to Text for particular workflows, I think it would make sense to add the instance (I can make a PR to do this).

[MichaelXavier]

What dependency would this add? I see several datatypes named ShortText on hackage.

[Boarders]

I meant this: https://hackage.haskell.org/package/text-short

[MichaelXavier]

Looks like a pretty popular library with a relatively limited dependency footprint. Feel free to submit an MR. Thanks!