[Feature Request] XDG Base Directory compliance

[ssnailed]

I'm a bit of a clean freak and like my home directory to be organized. Luckily for me, many applications will read the XDG_CONFIG_HOME variable and put their config files in that location. The one thing keeping me from switching from ferdium is this very minor detail.

I took a quick look over the code that determines the ~/.electromim/settings.json path, and it doesn't seem like it would be too difficult to implement a check for the XDG_CONFIG_HOME variable. Optimally, settings.json would be written to $XDG_CONFIG_HOME/electronim/settings.json.

If there is any interest for this feature I'd be happy to make a pull request.

[manusa]

If you want to make an attempt at contributing the fix, that'd be awesome :heart:. Keep in mind that the changes should be backwards compatible (feature-wise), and configurations stored in the legacy dir should still be taken into account.

Otherwise I can fix it.