Allow to see geometries of relations at specific versions

[matkoniecz]

For example see https://pewu.github.io/osm-history/#/relation/398785 or https://pewu.github.io/osm-history/#/relation/4344 - sadly geometry is not shown

No idea is it doable to add this support.

For practical use: someone proposed mass deletion of relations without members, I wanted to use this tool to investigate whether useful data is going to be lost