[Enhancement]: Improve PiSugar support

[kfezer]

Describe the bug
When trying to run inky_run.py and pysugar board is off, bet this error:

21-08-2024 10:44:54 | inkycal.main |  INFO: name : Weather size : 984x256 px
21-08-2024 10:44:54 | inkycal.main |  INFO: PiSugar support enabled.
21-08-2024 10:44:55 | inkycal.main |  INFO: PiSugar battery capacity: None%
Traceback (most recent call last):
  File "/home/inky/Inkycal/inky_run.py", line 43, in <module>
    asyncio.run(run())
  File "/usr/lib/python3.9/asyncio/runners.py", line 44, in run
    return loop.run_until_complete(main)
  File "/usr/lib/python3.9/asyncio/base_events.py", line 642, in run_until_complete
    return future.result()
  File "/home/inky/Inkycal/inky_run.py", line 18, in run
    inky = Inkycal(render=True, use_pi_sugar=True, shutdown_after_run=True)
  File "/home/inky/Inkycal/inkycal/main.py", line 168, in __init__
    if self.battery_capacity < 20:
TypeError: '<' not supported between instances of 'NoneType' and 'int'

To Reproduce
Steps to reproduce the behavior:

1. With rpi plugged in, run inky_run.py

Expected behavior
Should handle the error of type better.

[github-actions]

Hi there and welcome to Inkycal. Thanks for opening this issue. As this is your first issue in this repository, please read through the contributing guidelines

[aceisace]

Hi @kfezer and thanks for reporting the issue. Yes, it seems this needs some improvements as the battery level cannot be read if the PiSugar board is off. Would you be willing to help test this functionality as I do not use the PiSugar on my build?
If yes, I'll have a fix ready soon and will provide you with some instructions on how to test the fix. If it works for you, then this can be made public.

[aceisace]

Okay, I got a fix ready for this and it's now available. Please run the following to get the patch;

cd ~/Inkycal && source venv/bin/activate
git pull
python inky_run.py

If something shouldn't work as expected, please re-open the issue