Introduce `chain-spec-generator` and document Weight Generation process #338

Job	Run time
Extract tasks from matrix	7s
check-migrations (polkadot, polkadot-runtime, relay/polkadot, wss://polkadot-try-runtime-node.par...	12s
check-migrations (kusama, staging-kusama-runtime, relay/kusama, wss://kusama-try-runtime-node.par...	17s
check-migrations (asset-hub-kusama, asset-hub-kusama-runtime, system-parachains/asset-hubs/asset-...	11s
check-migrations (asset-hub-polkadot, asset-hub-polkadot-runtime, system-parachains/asset-hubs/as...	12s
check-migrations (bridge-hub-kusama, bridge-hub-kusama-runtime, system-parachains/bridge-hubs/bri...	13s
check-migrations (bridge-hub-polkadot, bridge-hub-polkadot-runtime, system-parachains/bridge-hubs...	11s
check-migrations (collectives-polkadot, collectives-polkadot-runtime, system-parachains/collectiv...	11s
check-migrations (encointer-kusama, encointer-kusama-runtime, system-parachains/encointer, wss://...	11s
	1m 45s

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