first cut at better build explanation

[masinter]

This is a first cut at trying to explain what's going on in all of these scripts. Not sure how useful this is.

At this level of detail, documentation belongs in the repo rather than the web site.

[blakemcbride]

Thanks for updating the instructions. While GitHub actions are all fine and dandy, linking Medley too tightly with GitHub will prematurely age Medley due to future GitHub changes (which are going to happen far, far sooner than changes to shell scripts.)

[masinter]

Maybe the part about using GitHub Actions belongs in a different document?

You can build Medley without GitHub or even without git installed.

The GitHub actions are for making a release for distribution.