✨ add uint256->int32 safecast

[chlwys]

Description

added an additional safecast for uint256 -> int32. Only added support for int32 because it's a more common number format, but the others could be added too

Checklist

Ensure you completed all of the steps below before submitting your pull request:

• [x] Ran forge fmt?
• [x] Ran forge snapshot?
• [x] Ran forge test?

Pull requests with an incomplete checklist will be thrown out.