Nightly / Alpha builds

[mikeee]

• Master/Main: 'nightly' builds (if changes have been pushed)
• Release branches - alpha builds (run nightly if changes have been pushed) + room for promotions to 'beta' if stability goals/milestones have been reached (potentially automated tests)

[mikeee]

@nelson-parente - Would love your input here, I'm planning to implement the above in this repo.