DOC: Converting from fiona CRS to pyproj.crs.CRS

[idanmiara]

I was struggling with finding the best way to convert between fiona CRS and pyproj CRS.

I think that the section https://pyproj4.github.io/pyproj/dev/crs_compatibility.html#converting-from-fiona-crs-to-pyproj-crs-crs needs to be updated with regards to https://github.com/Toblerity/Fiona/issues/714

Also, dc_crs is undefined: https://pyproj4.github.io/pyproj/dev/crs_compatibility.html#converting-from-pyproj-crs-crs-for-fiona https://pyproj4.github.io/pyproj/dev/crs_compatibility.html#preparing-pyproj-crs-crs-for-geopandas