added rpc polling time selector

frontend/src/atoms/rpc.ts

@@ -1,4 +1,4 @@
-import { selector } from 'recoil'
+import { atom, selector } from 'recoil'
 import { RPCClient } from '../lib/rpcClient'
 import { rpcHTTPEndpoint, rpcWebSocketEndpoint } from './settings'
 
@@ -12,3 +12,12 @@ export const rpcClientState = selector({
     ),
   dangerouslyAllowMutability: true,
 })
+
+export const rpcPollingTimeState = atom({
+  key: 'rpcPollingTimeState',
+  default: Number(localStorage.getItem('rpc-polling-time')) || 1000,
+  effects: [
+    ({ onSet }) =>
+      onSet(a => localStorage.setItem('rpc-polling-time', a.toString()))
+  ]
+})