Calculate building-to-building road width

[dabreegster]

Maybe if OS road width data is unavailable or insufficient, in dense areas, we can come up with a basic guess just from OSM data. Start with a road center-line, and project it left and right until we hit some building (or park or body of water). It'd be useful to compare results from this to anything higher quality from OS.

I started playing around with this at https://github.com/dabreegster/osm2svelte. The vector tiles loaded anyway for rendering can be used to grab building polygons (and probably road polylines too), making it convenient to iterate on this problem in JS, if that's the useful tech stack.