Log errors to a file

[Jacalz]

Checklist

• I have searched the issue tracker for open issues that relate to the same feature, before opening a new one.
• This issue only relates to a single feature. I will open new issues for any other features.

Is your feature request related to a problem?

On crashing, it would be good to see any errors that occurred even when not running Rymdport from a terminal. Always logging output to a log file should solve this.

Describe the solution you'd like to see.

Use a logger that prints to a file.

[Jacalz]

It might be nice to do this once we have Go 1.21 as the base and thus can use the new log/slog package. There will however be quite some time until we can use that as a base (currently just considering moving to Go 1.18 has minimum for v3.5.0) so we might have to either wait a long time or find a temporary solution.