Make it build with ghc-9.12

[erikd]

Just needs the base dependency bumped.

[erikd]

@hvr Ok if I edit the Hackage metadata on this to bump the base dependency?

[hvr]

@erikd if you're confident that the package's exposed API isn't broken or semantically changed by ghc-9.12's changes go ahead! Thanks!

[erikd]

Yep, been building and running with allow-newer: int-cast:base ever since this issue was raised.

[erikd]

And updated on Hackage.

[erikd]

Also, just to make sure, I editied the cabal file locally and built it and ran all the tests with ghc-9.12.

[erikd]

@hvr I am willing to become a co-maintainer of this package or you could hand it over to https://github.com/haskell-github-trust and I will help maintain it there.