Added endpoint for fetching server-side variables.

hooks/useConfig.js

@@ -0,0 +1,24 @@
+import { useEffect } from 'react';
+import useStore, { setConfig } from 'store/app';
+import useApi from 'hooks/useApi';
+
+let fetched = false;
+
+export default function useConfig() {
+  const { config } = useStore();
+  const { get } = useApi();
+
+  async function loadConfig() {
+    const { data } = await get('/config');
+    setConfig(data);
+  }
+
+  useEffect(() => {
+    if (!config && !fetched) {
+      fetched = true;
+      loadConfig();
+    }
+  }, []);
+
+  return config || {};
+}