chore(3.12.0): Add the installation manifest for 3.12.0 version (#4924) #1238

Job	Run time
frontend-checks	1m 31s
backend-checks	18s
get-envs	4s
docker-build-and-push-subscriber	8m 8s
docker-build-and-push-authentication-server	5m 42s
docker-build-and-push-event-tracker	10m 1s
docker-build-and-push-graphql-server	9m 43s
docker-build-and-push-frontend (litmusportal-frontend)	2m 24s
docker-build-and-push-frontend (litmusportal-frontend-path-litmuschaos, /litmuschaos)	2m 39s
	40m 30s

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