Tech demo: Vector tiles and pmtiles support

[podusowski]

It's super experimental, slow, needs some styling engine (protonmaps' json?).

Check out https://docs.protomaps.com/guide/getting-started for more information about pmtiles.

TODO

(only for this PR, the feature will still be super experimental, slow and generally considered as a tech demo)

• .pmtiles download snippet in README
• Zooming in.

[Swarkin]

this is awesome work! How customizable will the behaviour of the rendering engine be trough code, and how's the performance?
I pretty much built a very primitive Openstreetmap-data renderer on top of walkers from scratch for my app, but it is still missing multipolygon handling and proper area drawing. I'm interested in whether this PR could be replacing it, if the underlying rendering engine is styleable and performant enough.

[podusowski]

Well, is super slow, like barely usable, and it's missing tons of features, but I wanted to have something first. In general, I'd treat it like a glimpse into the far future. :)