Adds the option to display the battery icon automatically when connecting a battery device

I use a desktop, not a laptop, so the battery icon is correctly hidden automatically, but I sometimes use a bluetooth joystick and I like to check how much battery is charged, the battery widget shows this, but the icon remains hidden when connecting the joystick.

I did not change the default operation of Plasma, I just added a checkbox to allow the user to choose to automatically display the battery icon whenever a battery device is detected by this widget.

This video show icon automatic show and hidden when connect a bluetooth joystick: battery

Interface to change if enable that: