Add bluetooth headset battery's percentage in Ubuntu

This solution worked for me on Ubuntu 22.04. Follow this guide carefully as it could break the Bluetooth on your system.

1. Edit the following file as root:

/etc/bluetooth/main.conf

2. Add
   Experimental=true

   at the beginning of the file. It should look like this:

3. Save the file and quit the editor
4. Reload the Bluetooth service:

5. Install this GNOME extension: https://extensions.gnome.org//extension/3991/bluetooth-battery/
6. Edit the settings so they look like this, especially the
   % Source

   column: