WA-235 adding fetchThreshold action

src/routes/safe/store/actions/fetchThreshold.js

@@ -0,0 +1,12 @@
+// @flow
+import type { Dispatch as ReduxDispatch } from 'redux'
+import { type GlobalState } from '~/store/index'
+import { getSafeEthereumInstance } from '~/routes/safe/component/AddTransaction/createTransactions'
+import updateThreshold from './updateThreshold'
+
+export default (safeAddress: string) => async (dispatch: ReduxDispatch<GlobalState>) => {
+  const gnosisSafe = await getSafeEthereumInstance(safeAddress)
+  const actualThreshold = await gnosisSafe.getThreshold()
+
+  return dispatch(updateThreshold(safeAddress, actualThreshold))
+}