Just merged Favicon editing by UI into #Ecko, closing https://github.com/magicstone-dev/ecko/issues/245

I saw it work on a Heroku demo, and don't have the latest version running, so we could use some help running and testing the latest main branch, but the changes are pretty minimal for how cool the effect is.

We also have a procedure that needs testing for running a demo server of Ecko. https://github.com/magicstone-dev/ecko/pull/280