feat: add HTTP API GET for module variables

[GuideOTA]

resolves #2830

added an API GET command to return value of variables from modules rather than just custom variables

This is my first experience with GIT/TypeScript and honestly I have no Idea if what I added works or how to go about testing. any guidance would be appreciated, I am enthusiastic but ignorant.

[CLAassistant]

All committers have signed the CLA.

[GuideOTA]

Tested locally and the GET returns the value of module variables correctly

[thedist]

For better User Experience (and any developers who have to work on your code later), I would suggest changing the naming you're using in the API and docs for module, as that could lead to potential confusion as you're not getting the variable values of a module your getting the variable values of a specific instance of a module based on its label.

It's very possible that a user could have multiple connections to the same module, each with different values for the same variable, so why not make things clearer that the API requires the connection label.

For consistency it would be best if you adhere to the naming scheme already used within Companion.

[Julusian]

Looking good!
Could you try adding some unit tests in https://github.com/bitfocus/companion/blob/main/companion/test/Service/HttpApi.test.ts for this new endpoint? The tests for the custom-variable get will be a good reference of what cases to test and how it should behave

[GuideOTA]

Thanks for the guidance! working on this issue has been a big confidence booster for me. Hopefully the first of many contributions.