move to honojs instead of flight-path

[JakeChampion]

honojs is a small and very fast web-server library built primarily for edge-compute platforms such as Fastly and Cloudflare Workers.

I have a lot more experience using honojs now than I do flight-path and thought I'd take a moment to migrate polyfill.io over to it as the migration is rather low effort due to flight-path having a similar API ☺️