Add perspective for vector maps (pitch and bearing)

ok ... thanks @jan kellermann,
not sure how this could be useful, as the Leaflet Js core library doesn't support perspective (may it would with adds-on libraries?),
but indeed the MapLibreGL JS does, so may be Drupal Leaflet Views / Maps only with Tiles (and not loaded Features) might benefit from this ... (is't it?).
Going to merge this now into the 10.2.x dev, after just having reduced redundancy in leaflet.api.php documentation
This will be part of the next Drupal Leaflet 10.2.19 release ...