Provide a GitHub Action for comparing commit/commit changes in the report output

[runspired]

Said action would:

• generate the report
• fail if any reported measurements had increased since last checked-in report
• update any measurements that have decreased

This encourages forward-only maintenance of a codebase during migration periods.

[runspired]

I'll likely take a first stab at this but I suspect it should belong under the checkupjs org.

[rwjblue]

Seems neat!

[scalvert]

I like this. Happy to help hack on this with you!