Add additional metadata to global coverage tiles for filtering

[spwoodcock]

• Probably relies on Define queryables in PgSTAC #199 first.
• We need some better extracted metadata about imagery type, and number of bands in the STAC.
• Once we have this, at a minimum we can categorise the imagery into optical / DEM.
• We could then add filtering on the global coverage layer, based on metdata, e.g. only display the optical imagery coverage by default, with a toggle for DEM coverage.

We could extract details from COGs around here in the ingestion script:
https://github.com/hotosm/stactools-hotosm/blob/64a3a40fc9e693a0b079e315342b8400097bdaf4/src/stactools/hotosm/stac.py#L214-L217