Support Short schemas and args

[Fluxx]

I ran into a situation where I had a Short type that I needed a schema for, but Caliban didn't have one. This PR adds one which is implemented as a Scalar, along with an ArgBuilder for it. Few notes:

• My editor automatically trims training whitespace on save, so there are some whitespace changes. I am happy to remove them if you would like.
• I didn't see any specific tests for schemas so I didn't add any, but if you point me in the right direction I can add them.
• Let me know how to update docs. I think I only need to add the row to the table on the schema page, but I wasn't sure if the docs HTML checked in was automatically generated or not.

[ghostdogpr]

Looks good! Can you check the Scala 3 test that failed? Maybe it was using an implicit conversion which is no longer allowed?

[Fluxx]

I looked into it and you were correct. There does not appear to be an implicit short -> big decimal conversion in Scala3. I converted the value to an int first, which then uses the existing int -> big decimal conversion.

[ghostdogpr]

LGTM, thanks!