[Feature request] Log output to a file

[MXC1]

It'd be useful if slsk-batchdl would output logs and errors to a file.
If you have slsk-batchdl running on a cron job / scheduled task, you might not be able to see the output and whether everything was successful.

[fiso64]

This is normally done by redirecting the output to a file, e.g

sldl input >> log.txt 2>&1

although I'm now noticing that sldl does not behave correctly when the output is redirected. It exits almost immediately.