Add other entity types and use cron

Working on this. It should support any content entity and any configuration entity (some may be using configuration values for headless content).

For reference - we have a headless POC where some values are dictated from 'theme settings' for lack of better storage. This could have easily been a vanilla settings object.

Either way, the concept is, if anything about that theme changes, trigger a build (likely contains something in the header or footer, or may dictate some color values, etc).

I just realized the config entities are the actual objects, but not all the possible ones (like Views not being listed out). This will need more work.