docs(redis-smq): improve message storage documentation and class refe… #567

Job	Run time
list-packages	4s
tests (ubuntu-latest, 20, redis-smq-common)	3m 30s
tests (ubuntu-latest, 20, redis-smq)	10m 58s
tests (ubuntu-latest, 20, redis-smq-web-ui)	1m 2s
tests (ubuntu-latest, 20, redis-smq-rest-api)	3m 15s
	18m 49s

Provide feedback