Adds Snowbridge to Rococo runtime (#2522)

# Description

Adds Snowbridge to the Rococo bridge hub runtime. Includes config
changes required in Rococo asset hub.

---------

Co-authored-by: Alistair Singh <alistair.singh7@gmail.com>
Co-authored-by: ron <yrong1997@gmail.com>
Co-authored-by: Vincent Geddes <vincent.geddes@hey.com>
Co-authored-by: claravanstaden <Cats 4 life!>

cumulus/polkadot-parachain/src/chain_spec/bridge_hubs.rs

@@ -231,6 +231,10 @@ pub mod rococo {
 			"bridgeWestendMessages": {
 				"owner": bridges_pallet_owner.clone(),
 			},
+			"ethereumSystem": {
+				"paraId": id,
+				"assetHubParaId": 1000
+			}
 		})
 	}
 }