Feature: Initialize simple logger with custom logging-backend.

[fslongjin]

Feature: Initialize simple logger with custom logging-backend.

[fslongjin]

ping

[borntyping]

I'm very conflicted on this PR - it's cleanly implemented and well documented, but it isn't something I want to include in a logging library that aims to be very simple (and low-effort to maintain) so I don't plan to merge it. Thank you for your efforts anyway!

(More specifically, simple_logger is already a logging backend for the log library, and makes a lot of choices that make it very specific to terminal output that wouldn't make sense for any other backend like files or external services. If you're partically intrested in using the output format in another backend, splitting the text formatting out from printing so it could be called from another library might make sense. Or if this is something you have plans to expand on, I absolutely endorse forking it and using it as a base to build on.)