Watch Later Shortcuts, Global Switch, Logo on the Webpage

• More comprehensive fix to shortcuts still working when typing in an input field.
• Explicitly Excluded YouTube Studio from this extension.
• Now we can also unsubscribe from the channel.
• Playlists are also scrollable through the extension.
• Add videos to the Watch Later Playlist with Ctrl + y.
  • Access the Watch Later playlist through Ctrl + ..
• Global switch for the whole extension.
• Now the extension logo appears right next to the YouTube logo, signaling that the extension is on.