Redirect from /:changeset_id to /changesets/:changeset_id isn't working

[jake-low]

When you load a URL like https://osmcha.org/155530622, the frontend redirects itself to https://osmcha.org/changesets/155530622, but the map fails to load until you refresh the page manually.

This is related to but distinct from #481. Ideally any of the three URL formats (/:id, /changeset/:id, and /changesets/:id) would work and all redirect to the same canonical URL.