document `useQueryCacheInvalidator`

explains why `chainId` is pulled directly from the store.

src/state/application/updater.ts

@@ -8,9 +8,14 @@ import { useActiveWeb3React } from '../../hooks/web3'
 import { updateBlockNumber, updateChainId } from './actions'
 
 function useQueryCacheInvalidator() {
-  const chainId = useAppSelector((state) => state.application.chainId)
   const dispatch = useAppDispatch()
   
+  // subscribe to `chainId` changes in the redux store rather than Web3
+  // this will ensure that when `invalidateTags` is called, the latest
+  // `chainId` is available in redux to build the subgraph url
+  const chainId = useAppSelector((state) => state.application.chainId)
+
+
   useEffect(() => {
     dispatch(api.util.invalidateTags([CHAIN_TAG]))
   }, [chainId, dispatch])