Ingest Mbed mercurial repositories

As reported by @pabs on IRC:

<p​abs3> https://os.mbed.com/ contains hg repos, and is shutting down by July 2026 https://os.mbed.com/blog/entry/Important-Update-on-Mbed/
<p​abs3> example repo https://os.mbed.com/users/mbed_official/code/mbed/
<p​abs3> hmm no easy way to enumerate usernames yet :/
<p​abs3> running an ArchiveBot job to capture the site, which should help
<p​abs3> there is https://os.mbed.com/activity/code/ but it does not give all repos, only 3 pages