Housekeeping: Improve docs and update outdated references to point to MapLibre

[m0nac0]

This PR does quite some housekeeping in updating outdated references from mapbox to maplibre, mostly in doc comments in the web sub-package.

This obviously seems like a quite huge PR, but I think for the review it is sufficient to take a short look at the simple renamings (they are in separate commits and were done with IDE tooling) and maybe a cursory look at the doc comments.
The web documentation changes are quite unspectacular and probably barely anyone ever looks at the web-plugin docs, but I think we needed to do this housekeeping at some point.

• updated documentation:

  • especially added new docs for the maplibre_gl library and MaplibreMapControler and MaplibreMap, as well as removing outdated comments in many places and adding some new ones to help new users better understand the plugin
  • the updates for the web documentation comments were also mostly done with a series of replace-all, sometimes manually updated to reflect the online API reference of MapLibre JS

• the only "code changes" are a couple of (simple) renamings:

  • main plugin: renamed src/mapbox_map.dart to src/maplibre_map.dart
  • main plugin: renamed MapboxColorConversion to MapLibreColorConversion
  • main plugin: maplibreGlPlatform variable (the class was already renamed in the past) in controller.dart
  • main plugin: _MaplibreMapOptions class
  • web: "library maplibre" at the top of most files
  • web: MapboxMapJsImpl to MapLibreMapJsImpl
  • web: MapboxMapOptionsSink to MapLibreMapOptionsSink

All renamings were done only with the IDE renaming function. There are no functional changes and no changes in the public API, only some internal renamings and updated doc comments. (This can also be seen by the fact that the example app needs no updates, only two internal variables were renamed).

Nearly all remaining references to mapbox are in the android or ios directories.