feat(governance): add OpenGov v2 indexer for referenda, votes, delegations

Index convictionVoting and referenda pallet data to support PezWallet
governance UI — referendum tracking, casting votes, delegation stats,
and delegator vote propagation.

src/index.ts

@@ -5,4 +5,5 @@ export * from "./mappings/PoolRewards";
 export * from "./mappings/Transfers";
 export * from "./mappings/NewEra";
 export * from "./mappings/PoolStakers";
+export * from "./mappings/Governance";
 import "@pezkuwi/api-augment";