Battery Status Plus per 79King

Display battery status on the extension icon and popup page, and support custom notifications.

State of the extension icon:
● Green color: power level > 15%, Red color: power level <= 15%
● ⚡️flag: charging or fully charged, without ⚡️flag: not charged
● The battery icon itself reflects the overall power level
● Hover over the icon to display battery percentage

The popup page displays detailed information, and you can set whether to show battery percentage on the extension icon.