Add support for `Scheduler#postTask` #292

Job	Run time
Validate Steward Config (ubuntu-latest)	8s
Build and Test (ubuntu-latest, 2.11.12, temurin@8, ciNode)	1m 16s
Build and Test (ubuntu-latest, 2.11.12, temurin@8, ciFirefox)	1m 32s
Build and Test (ubuntu-latest, 2.11.12, temurin@8, ciChrome)	1m 15s
Build and Test (ubuntu-latest, 2.11.12, temurin@8, ciJSDOMNodeJS)	1m 6s
Build and Test (ubuntu-latest, 2.12.16, temurin@8, ciNode)	1m 15s
Build and Test (ubuntu-latest, 2.12.16, temurin@8, ciFirefox)	1m 15s
Build and Test (ubuntu-latest, 2.12.16, temurin@8, ciChrome)	1m 5s
Build and Test (ubuntu-latest, 2.12.16, temurin@8, ciJSDOMNodeJS)	1m 17s
Build and Test (ubuntu-latest, 2.13.7, temurin@8, ciNode)	1m 11s
Build and Test (ubuntu-latest, 2.13.7, temurin@8, ciFirefox)	1m 20s
Build and Test (ubuntu-latest, 2.13.7, temurin@8, ciChrome)	1m 31s
Build and Test (ubuntu-latest, 2.13.7, temurin@8, ciJSDOMNodeJS)	1m 12s
Build and Test (ubuntu-latest, 3.1.3, temurin@8, ciNode)	1m 12s
Build and Test (ubuntu-latest, 3.1.3, temurin@8, ciFirefox)	1m 8s
Build and Test (ubuntu-latest, 3.1.3, temurin@8, ciChrome)	1m 0s
Build and Test (ubuntu-latest, 3.1.3, temurin@8, ciJSDOMNodeJS)	1m 1s
Publish Artifacts	0s
	19m 44s

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