Add badge for examples' testing
.. image:: https://github.com/PMEAL/porespy/workflows/CI/badge.svg
:target: https://github.com/PMEAL/porespy/actions
+.. image:: https://github.com/PMEAL/porespy/workflows/Examples/badge.svg
+ :target: https://github.com/PMEAL/porespy/actions
+
.. image:: https://codecov.io/gh/PMEAL/PoreSpy/branch/master/graph/badge.svg
:target: https://codecov.io/gh/PMEAL/PoreSpy
