helper function to infer data dir

[FlorisCalkoen]

@2320sharon, feel free to accept/reject this change. You might find it helpful in determining the CoastSeg directory path. The function returns a pathlib object, which automatically handles different operating systems. You can find the implementation here.

I have temporarily left a few lines inside if __name__ == "__main__", so you can quickly check how/if it works.

This might resolve #246 (comment)

[FlorisCalkoen]

Btw, apologies for formatting some of your code.. my automatic formatting was still on.

[2320sharon]

@FlorisCalkoen

Thank you for you this code I'll add this to CoastSeg so that it can automatically read from the correct data directory. The code in this PR works great!

[2320sharon]

Thank you for this PR Floris. I merged in your pull request to add you to the list of contributors, but I ended up moving your code out of common.py to core_utilities.py. This code is super helpful to have in CoastSeg, so thank you for providing it.