chore: reintroduce stale bot #2454

Job	Run time
web-wasm (tests)	4m 39s
web-wasm (packages/cloud_firestore/cloud_firestore/example)	4m 22s
web (packages/cloud_firestore/cloud_firestore/example)	5m 45s
web-app-check	3m 11s
web (tests)	4m 43s
	22m 40s

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