Automated Github Build Actions

[nicholas-maltbie]

Description

Added github action for building the server for windows, linux, and OSX as well as run unit tests.

Using these resources and added UNITY_SECRETS to github settings (not a committed file)

https://github.com/marketplace/actions/unity-builder

https://unity-ci.com/docs/github/getting-started

How Has This Been Tested?

Tested with example action https://github.com/nicholas-maltbie/PropHunt/actions/runs/233363005

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes

(No testing framework setup yet so ignore the last two)

Closes #28
Closes #21