Brew: Improve type checking documentation

[MikeMcQuaid]

Extracted from https://github.com/Homebrew/brew/issues/8991

• [ ] Improve the documentation in https://docs.brew.sh/Typechecking
• [ ] Improve tooling/CI output (e.g. brew typecheck) to reference documentation (and vice-versa)
• [ ] Consider/investigate improving naming here with some of our own aliases to be Type::Signature

[vidusheeamoli]

I'm on it!

[reitermarkus]

Consider/investigate improving naming here with some of our own aliases to be Type::Signature

I don't think this will improve readability/understandability when people read Sorbet documentation which only ever mentions T, T::Sig and other methods on the T module but we choose to use a differing name.

[MikeMcQuaid]

I don't think this will improve readability/understandability when people read Sorbet documentation which only ever mentions T, T::Sig and other methods on the T module but we choose to use a differing name.

It'll improve readability for people who read our code but haven't read Sorbet documentation. It is not a realistic expectation that this will happen for everyone who reads Homebrew's code. We should aim to improve the readability of Homebrew's code to newcomers.