USB-C power supply might not be reported

[rwappler]

Describe the bug
I am sitting here on a Thinkpad T14 AMD Gen 2a. The power supply is connected via USB-C. However, kernel does not report it as USB-Device or power delivery. Therefore /sys/class/power_supply/*/online will never be 1. Therefore laptop-mode will always be active.

Fix suggested in #192

To Reproduce
Steps to reproduce the behavior:

1. Use power supply via USB-C that is not detected by the kernel
2. run laptop_mode status
3. laptop-mode will always be active.

Expected behavior

In absence of an AC power supply, the battery status should be used, to determine, whether to activate laptop-mode or not. I.e. activate it based on BATTERY_NOT_DISCHARGING

Screenshots
n/a

Important Information:

• Distribution: gentoo
• Linux Kernel: 6.0.3 x86_64
• Laptop Mode Tools version: 1.74
• Desktop Environment, if any: kde plasma
• Relevant System Logs: n/a
• Laptop Mode Tools verbose logs: n/a

Additional context
Add any other context about the problem here.