Add to Stackage LTS

[kamek-pf]

Hello !

I noticed tz is unavailable in the current Stackage LTS.
Adding a package looks simple enough, the Stackage team recommends maintainers to add their own packages :
https://github.com/commercialhaskell/stackage/blob/master/MAINTAINERS.md#adding-a-package

Would you mind taking a look ?

[ysangkok]

Seems like the current reason for not having it in Stackage Nightly is that the flag template-haskell is on by default and forbids GHC 9. https://github.com/commercialhaskell/stackage/blob/f3bebb771742688c3a934396656b55a69ee80584/build-constraints.yaml#L6568

Using Nightly, I can only turn off that flag by adding an extra-dep though.