Improve doc theme and update README #4599

Job	Run time
Build docker image	4m 8s
Build debian package (bionic)	2m 58s
Build debian package (focal)	3m 54s
Python Unittests (focal-3.8, tests)	5m 49s
Build debian package (jammy)	5m 55s
Python Unittests (focal-3.8, tests_nds)	5m 50s
Python Unittests (jammy-3.10, tests)	5m 49s
Python Unittests (jammy-3.10, tests_nds)	5m 49s
Tests E2E docker	1m 47s
Upload coverage to codecov	1s
Tests E2E 20.04	1s
Publish (on release only)	1s
	42m 2s

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