Go binding: Finish implementation of the Maybe module

[michelchan]

Go binding: Finish implementation of the Maybe module

Item	Detail
Binding	Go
Module	Morphir.SDK.Maybe
Relevant Morphir.IR.SDK module	Morphir.IR.SDK.Maybe
Relevant morphir-jvm code	morphir.sdk.Maybe
Relevant Elm Module	Maybe

Provide a Go lang implementation of the Morphir.SDK.Maybe module for Morphir.SDK.

The implementation should include all the functionality for Maybe as well as tests (we are willing to have this split across PRs).

Please place it here: https://github.com/finos/morphir/tree/features/polyglot-morphir/corelib/go/morphir/sdk/