Improved search and mobile support for the Device OS Firmware API docs

The previous single-page version is still available, however, the same source now generates a separate set of docs arranged into small chunks.

This will generate much better search results both for our built-in search but also eventually in external search engines like Google.

The internal search now produces far more accurate results, and you’re brought right to the topic instead of the top of the huge firmware API reference. It also loads much faster. Searching for BLE.advertise returns a meaningful result now!

On mobile (phone and tablet), swipe and edge-tap are now supported for browsing the firmware API reference docs.

Helpful hint: In the search box at the top of the docs, hitting return brings up an overlay with more search results. For reasons I do not fully understand, when you search for certain API calls that are not an English word (like publishVitals) the results only show up in the overlay page and not in the autocomplete.