Add support for `Scheduler#postTask` #275

Job	Run time
Validate Steward Config (ubuntu-latest)	10s
Build and Test (ubuntu-latest, 2.11.12, temurin@8, ciNode)	1m 7s
Build and Test (ubuntu-latest, 2.11.12, temurin@8, ciFirefox)	1m 29s
Build and Test (ubuntu-latest, 2.11.12, temurin@8, ciChrome)	1m 17s
Build and Test (ubuntu-latest, 2.11.12, temurin@8, ciJSDOMNodeJS)	1m 17s
Build and Test (ubuntu-latest, 2.12.16, temurin@8, ciNode)	1m 13s
Build and Test (ubuntu-latest, 2.12.16, temurin@8, ciFirefox)	1m 27s
Build and Test (ubuntu-latest, 2.12.16, temurin@8, ciChrome)	1m 4s
Build and Test (ubuntu-latest, 2.12.16, temurin@8, ciJSDOMNodeJS)	1m 6s
Build and Test (ubuntu-latest, 2.13.7, temurin@8, ciNode)	55s
Build and Test (ubuntu-latest, 2.13.7, temurin@8, ciFirefox)	1m 29s
Build and Test (ubuntu-latest, 2.13.7, temurin@8, ciChrome)	58s
Build and Test (ubuntu-latest, 2.13.7, temurin@8, ciJSDOMNodeJS)	55s
Build and Test (ubuntu-latest, 3.1.3, temurin@8, ciNode)	56s
Build and Test (ubuntu-latest, 3.1.3, temurin@8, ciFirefox)	1m 9s
Build and Test (ubuntu-latest, 3.1.3, temurin@8, ciChrome)	1m 8s
Build and Test (ubuntu-latest, 3.1.3, temurin@8, ciJSDOMNodeJS)	1m 0s
Publish Artifacts	0s
	18m 40s

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