Spotify Playback Speed

Adds a button and menu to manipulate playback speed on Spotify Web.

Quickly change playback speed on Spotify Web because some songs just sound better faster or slower. -- Release notes -- March 2025: * Fixed playback rate not being set right away when changing value February 2025: * Fixed a bug where menu is hidden by 'Now Playing View' and 'Queue' sidebar 2023: * Fixed preserve pitch setting not being remembered * Fixed playback rate not being set right away when changing value * Added more checks to ensure a bug causing playback speed of 0 doesn't get set. * Fixed a bug from a recent Spotify Web update that caused the extension to not show up. * Fixed a bug that was causing potential audio artifacts due to unintended playback speed changes coming from a recent Spotify Web update. - Big thanks to Kamil K. for the help!