Check documentation on CI #1341

Job	Run time
build_and_test (ubuntu-latest, Release, roslyn3.8)	3m 6s
check_documentation	15s
build_and_test (ubuntu-latest, Release, roslyn4.2)	3m 1s
compute_package_version	3s
build_and_test (ubuntu-latest, Release, roslyn4.4)	2m 55s
build_and_test (ubuntu-latest, Release, roslyn4.6)	3m 4s
build_and_test (ubuntu-latest, Release, roslyn4.8)	3m 1s
build_and_test (ubuntu-latest, Release, default)	3m 5s
build_and_test (windows-latest, Release, roslyn3.8)	8m 6s
build_and_test (windows-latest, Release, roslyn4.2)	7m 16s
build_and_test (windows-latest, Release, roslyn4.4)	6m 57s
build_and_test (windows-latest, Release, roslyn4.6)	7m 41s
build_and_test (windows-latest, Release, roslyn4.8)	7m 3s
build_and_test (windows-latest, Release, default)	7m 49s
create_nuget	2m 17s
validate_nuget	47s
deploy	0s
create_release	0s
	1h 6m 26s

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