URL does not update when layer is chosen

1. Visit https://geojson.io/#map=18/24.177045/120.720867
2. Move the map around.
3. Observe the URL in the browser URL bar updating.
4. Now see the bar at the bottom of the screen,
`Standard Standard Satellite Standard Light Standard Dark Outdoors OSM`
and pick one.
5. Alas, the URL does not update.
6. Contrast this with OSM.ORG website, where the URL will contain the layer we chose. That makes it possible to share maps featuring any layer, not just the standard layer!
7. Same problem with the `Globe Mercator` buttons.

Reproduce the issue at the linked geojson.io map by moving the map, selecting each bottom-bar layer, and switching between the Globe Mercator buttons. Trace the URL state handling for those controls and compare it with the existing map-position URL updates. Done means the selected layer and projection are preserved in the browser URL and can be shared.

Written by the indexing model from the issue text.