Add PMTiles support

[m-mohr]

Depends on:

• Added PMTiles #17 stac-extensions/web-map-links#18
• Add .js to imports protomaps/PMTiles#240
• js: FetchSource takes optional custom headers protomaps/PMTiles#112

[bdon]

I think we should either:

• mirror the data in this GH repo or in some CORS-friendly bucket for other STAC assets
• I can mirror this at a stable url like r2-public.protomaps.com/stac/foo.pmtiles

[m-mohr]

This would be great, indeed!

[bdon]

LGTM, examples work for me after I published ol-pmtiles 0.2.0

[bdon]

@m-mohr are we blocked merging this until protomaps/PMTiles#112 is done?

It seems like in its current state it will only support PMTiles in public buckets with appropriate CORS headers.

If we change ol-pmtiles to take PMTiles objects instead of string URLs, we can implement auth via a custom Source that lives in ol-stac and is tied to the signing capabilities of ol-stac

Any rework of the PMTiles js itself (not ol-pmtiles) has a longer timeline...

[m-mohr]

Thanks. Not blocking, I just need to document it.

But I also still want to find a better way to configure the sources generally, because the current way with so many get...SourceOptions callbacks doesn't scale very well...

[m-mohr]

I refactored the source creation. So as long as I'd be able to pass the headers via the source options, I'd be fine.
See also protomaps/PMTiles#112 (comment)

Anyway, this can be merged, I think. The way it's handled here is now pretty much independant of the underlying implementation. Implementors need to check how the source options look like and adapt their implementation accordingly.