Add Websockets support #4467

Job	Run time
check format (ubuntu-latest / nightly)	14s
check format (ubuntu-latest / nightly)	14s
check docs (ubuntu-latest / stable)	1m 4s
check docs (ubuntu-latest / stable)	1m 4s
check examples (ubuntu-latest / stable)	59s
check examples (ubuntu-latest / stable)	59s
check feature flags (ubuntu-latest / stable)	15m 51s
check feature flags (ubuntu-latest / stable)	15m 51s
check licenses (ubuntu-latest / stable)	23s
check licenses (ubuntu-latest / stable)	23s
check linter (ubuntu-latest / stable)	1m 36s
check linter (ubuntu-latest / stable)	1m 36s
check minimal versions of transitive dependencies (ubuntu-latest / stable)	1m 36s
check minimal versions of transitive dependencies (ubuntu-latest / stable)	1m 36s
check minimal supported rust version (ubuntu-latest / msrv)	43s
check minimal supported rust version (ubuntu-latest / msrv)	43s
check spelling (ubuntu-latest / nightly)	5m 51s
check spelling (ubuntu-latest / nightly)	5m 51s
test (ubuntu-latest / stable)	6m 41s
test (ubuntu-latest / stable)	7m 22s
test (macos-latest / stable)	9m 8s
test (macos-latest / stable)	9m 8s
test (windows-latest / stable)	10m 53s
test (windows-latest / stable)	10m 53s
	1h 50m 39s

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