chore(docs): add message hub client example #903

Job	Run time
dco / check	4s
reuse / test	8s
warmup-caches / stable / build	2m 21s
warmup-caches / nightly / build	2m 23s
warmup-caches / beta / build	2m 32s
e2e-test / e2e-test	5m 39s
multi-platform / windows-latest / stable / test	3m 50s
test / ubuntu / stable	1m 56s
check / beta / clippy	1m 8s
check / stable / clippy	1m 30s
test / ubuntu / stable / coverage	1m 27s
test / ubuntu / beta	1m 53s
check / stable / fmt	24s
check / ubuntu / 1.78	1m 14s
check / nightly / doc	1m 25s
check / stable / for-publish	1m 2s
check / ubuntu / stable / minimal-versions	1m 34s
check / ubuntu / stable / features	5m 16s
check / stable / semver	0s
	35m 46s

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