wradlib/wradlib: wradlib-release v1.13.0

tested with a build matrix for Python 3.7, 3.8 and 3.9 under conda-forge channel environment on linux OS (GitHub Actions) tested with Python 3.9 under conda-forge channel on MacOSX (GitHub Actions) tested with Python 3.9 under conda-forge channel on Windows OS (GitHub Actions) tested wradlib-notebooks creation for linux OS (GitHub Actions) with Python 3.9 What's Changed ENH: add iris/sigmet xarray backend by @kmuehlbauer in https://github.com/wradlib/wradlib/pull/520 ENH: Iris xarray reader, fix GAMIC reader by @kmuehlbauer in https://github.com/wradlib/wradlib/pull/523 FIX: catch dt.accessor TypeError by @kmuehlbauer in https://github.com/wradlib/wradlib/pull/529 FIX: remove fix_cyclic, fix deprecated matplotlib functions by @kmuehlbauer in https://github.com/wradlib/wradlib/pull/530 ENH: add rainbow xarray backend by @kmuehlbauer in https://github.com/wradlib/wradlib/pull/522 ENH: Optionalize dependencies by @kmuehlbauer in https://github.com/wradlib/wradlib/pull/531 Full Changelog: https://github.com/wradlib/wradlib/compare/1.11.0...1.13.