add runtime release guidelines in the README and update the PR templa… #2307

Job	Run time
Extract tasks from matrix	3s
check-migrations (polkadot, polkadot-runtime, relay/polkadot, wss://try-runtime.polkadot.io:443, ...	21m 49s
check-migrations (kusama, staging-kusama-runtime, relay/kusama, wss://try-runtime-kusama.polkadot...	16m 41s
check-migrations (asset-hub-kusama, asset-hub-kusama-runtime, system-parachains/asset-hubs/asset-...	18m 12s
check-migrations (asset-hub-polkadot, asset-hub-polkadot-runtime, system-parachains/asset-hubs/as...	40m 40s
check-migrations (bridge-hub-kusama, bridge-hub-kusama-runtime, system-parachains/bridge-hubs/bri...	9m 25s
check-migrations (bridge-hub-polkadot, bridge-hub-polkadot-runtime, system-parachains/bridge-hubs...	15m 18s
check-migrations (collectives-polkadot, collectives-polkadot-runtime, system-parachains/collectiv...	9m 56s
check-migrations (coretime-kusama, coretime-kusama-runtime, system-parachains/coretime/coretime-k...	9m 5s
check-migrations (people-kusama, people-kusama-runtime, system-parachains/people/people-kusama, w...	9m 23s
check-migrations (people-polkadot, people-polkadot-runtime, system-parachains/people/people-polka...	11m 25s
check-migrations (encointer-kusama, encointer-kusama-runtime, system-parachains/encointer, wss://...	9m 43s
All migrations passed	1s
	2h 51m 41s

Provide feedback