Implement the Month Module of the Morphir IR SDK

Is your feature request related to a problem? Please describe.
Morphir's SDK seeks to have parity with much of elm/core and should have full parity with elm/core Month.

Describe the solution you'd like
Implement the functions in [elm/core Month](https://github.com/finos/morphir-elm/blob/main/src/Morphir/IR/SDK/Month.elm) and add tests. Over time we will add more functionality here, but this is a good start.

Describe alternatives you've considered
N/A

Additional context
N/A

Start by comparing the linked elm/core Month.elm implementation with the repository's Morphir IR SDK module and test layout. Implement the requested Month functions and add tests demonstrating parity with the referenced Elm module; done means the supported functions are covered by passing tests.

Written by the indexing model from the issue text.