Add Contact support button (#45)

src/index.tsx

@@ -10,6 +10,7 @@ fetch("config.json")
   .then(res => res.json())
   .then(props => {
     storage.setItem("as_managed_users", JSON.stringify(props.asManagedUsers));
+    storage.setItem("support_url", props.supportURL);
     return createRoot(document.getElementById("root")).render(
       <React.StrictMode>
         <AppContext.Provider value={props}>