Changesets: Add bounding box highlight, zoom to fit button

[danieldegroot2]

What feature would you like to see added?

Add optional changeset bounding box highlight (toggle) additionally you could add a zoom to fit button

Currently, the default zoom is static, it does seem to change with changeset size. Example https://osmcha.org/changesets/169422078 shows only part of changeset. (Chrome on Windows 10)

Sparse changesets are somewhat confusing, but there is only so much there. Example https://osmcha.org/changesets/169422077

Related #686/#639/#401.

Why would this be useful to you or other users?

Allow to get a quick overview of everything.

Currently, user has to manually check if they see everything when they zoom out, or look at it on OSM/Achavi/...