Improve how argopy follows Argo software development guidelines

Such guidelines are developed as part of the Euro-Argo ONE project here: https://github.com/euroargodev/software_guidelines/issues

I figured that I could list what could be interesting to implement at Argopy.

I will use this issue as a place holder to point toward for more specific sub-issues.

Start by reviewing the Euro-Argo software guidelines issue linked in the description, then identify which specific guideline items apply to Argopy. This placeholder is not ready to implement until those items are split into concrete sub-issues with defined completion criteria.

Written by the indexing model from the issue text.