Support Python 3.10
Python 3.10 has been released the 2021-10-04. It seems that every dependencies support it. Also Python 3.6 support will end on 2021-12-23, so I think we could remove it at the same time. This keeps to 4 the number of Python version supported. Later when we will drop 3.7 and have only the new yearly releases, we will keep 5 versions as they are supported 5 years.