Adds buttons for MusicBrainz, Harmony, ISRC Hunt and SAMBL to Spotify.
Based on the original script by RustyNova which can be found at https://github.com/RustyNova016/MusicBrainz-UserScripts/blob/main/spotify-musicbrainz-import.user.js
This version was reworked and notably adds buttons for ISRC Hunt, ListenBrainz and SAMBL. a-tisket was removed
