Create a morphir-elm sbt plugin that is tasked with wrapping the morphir-elm CLI

## Feature Request

Create a morphir-elm sbt plugin that is tasked with wrapping the morphir-elm CLI

### Description of Problem:
Morphir is capable of using its `morphir-elm make`, `morphir-elm gen`, and `morphir-elm test` commands to generate code and run tests.

We have a need to generate Morphir IR and use `morphir-elm`'s code generation capability within Scala builds.

We should create an SBT plugin that allows us to accomplish this.

### Potential Solutions:

While we can bootstrap this process by doing SBT specific file and process creation, it should be noted we will want to accomplish the same behavior for `Mill` and `scala-cli` (and possibly Gradle).

No files or tests are named. Start by examining how morphir-elm make, gen, and test would need to be invoked from an SBT plugin, then define the plugin's scope and behavior; done means Scala builds can use those commands to generate Morphir IR, generate code, and run tests.

Written by the indexing model from the issue text.