Make MBID extraction more robust

[kellnerd]

https://github.com/RustyNova016/MusicBrainz-UserScripts/blob/b6a269924e9a4f93d07f56c0b3a96558a280365c/musicbrainz-go-to-harmony.user.js#L28 leads to weird requests like http://harmony.pulsewidth.org.uk/release/actions?release_mbid=add-cover-art?tport=8000 for any page whose URL doesn't end with the MBID.

[RustyNova016]

I split the url on "/" and return the last element so yeah, those break. I'll fix it later Edit: GH mobile doesn't give code snippets- My comment is irelevent...