chore(docs): add message hub client example #929

Job	Run time
dco / check	2s
reuse / test	9s
e2e-test / e2e-test	6m 23s
warmup-caches / stable / build	1m 59s
warmup-caches / beta / build	1m 27s
multi-platform / windows-latest / stable / test	5m 12s
warmup-caches / nightly / build	1m 45s
test / ubuntu / stable	1m 16s
test / ubuntu / stable / coverage	2m 4s
test / ubuntu / beta	1m 22s
check / ubuntu / 1.78	1m 29s
check / stable / clippy	1m 13s
check / stable / fmt	7s
check / ubuntu / stable / minimal-versions	1m 1s
check / nightly / doc	55s
check / ubuntu / stable / features	5m 23s
check / stable / for-publish	1m 20s
check / beta / clippy	1m 3s
check / stable / semver	0s
	34m 10s

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