[Feature request]: Pass config file as a commandline argument

[aktaboot]

Please describe your feature request

Having this feature would make it more convenient to run it as a system-wide service.

[maximbaz]

Just to add that in order to achieve running it as a system-wide service, more changes would be needed, e.g. wluma stores training data in $XDG_DATA_HOME.

wluma/src/predictor/data.rs

Lines 58 to 59 in 8df0b8e

	Ok(xdg::BaseDirectories::with_prefix("wluma")?
	.create_data_directory("")?

May I ask what is your motivation for running it as a system-wide service?