Add Github CI action to update Dockerhub description from README #239

Job	Run time
Build, test and push (amd64, py27,py36,py38,py39,py310,py311,py312,py313,py314,pypy,pypy39,pypy310)	3m 28s
Build, test and push (arm64, py312)	46m 9s
Build, test and push (ppc64le, py38,py311)	11m 54s
Build, test and push (s390x, py39,py310,py312)	13m 17s
Update Dockerhub description	3s
Update and test manifests	1m 53s
	1h 16m 44s

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