Offer alternative method to automatically skip update check at startup that doesn't require manual response to an input()

[simonhollingshead]

I'm running this bot as a systemd service on my VPS, so it starts automatically if the machine needs to reboot for a kernel upgrade.

Waiting for user supplied responses using input() is therefore not a great idea, it'll just make the launch hang.

Therefore, I'd like to propose that the version prompt (https://github.com/Reloisback/Whiteout-Survival-Discord-Bot/blob/main/main.py#L168) should be able to be skipped with a flag (i.e. using argparse). It's probably right that you still do the check and log the fact that you've checked (so an administrator can know that they need to do an update at a time that suits them), but you could offer --no-update and --always-update to act like a default 'y' or 'n' press to the request.

[simonhollingshead]

This request would also be solved by the environment variable proposal in #23, I don't mind it being in the env instead of being a flag.