Update README, containers, CI for software.eessi.io #348

Job	Run time
test-playbook (stratum0, rockylinux-8)	3m 35s
test-playbook (stratum0, ubuntu-20.04)	1m 51s
test-playbook (stratum0, ubuntu-22.04)	1m 42s
test-playbook (stratum1, rockylinux-8)	3m 1s
test-playbook (stratum1, ubuntu-20.04)	2m 25s
test-playbook (stratum1, ubuntu-22.04)	2m 9s
test-playbook (localproxy, rockylinux-8)	3m 3s
test-playbook (localproxy, ubuntu-20.04)	1m 59s
test-playbook (localproxy, ubuntu-22.04)	1m 59s
test-playbook (client, rockylinux-8)	3m 1s
test-playbook (client, ubuntu-20.04)	1m 53s
test-playbook (client, ubuntu-22.04)	1m 28s
	28m 6s

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