Undocumented System Event `power_source` to be added

[technobly]

Since 0.8.0 / 1.0.0

power_source system event notified when the PMIC source changes

Parameter will be one of the following ENUMs

typedef enum {
    POWER_SOURCE_UNKNOWN = 0,
    POWER_SOURCE_VIN = 1,
    POWER_SOURCE_USB_HOST = 2,
    POWER_SOURCE_USB_ADAPTER = 3,
    POWER_SOURCE_USB_OTG = 4,
    POWER_SOURCE_BATTERY = 5
} power_source_t;