Non-functional changes.

Author: DovydasNavickas

src/app.tsx

@@ -1,8 +1,7 @@
 import React, { useState, useEffect, ErrorInfo } from "react";
 import ReactDOM from "react-dom";
-import { Test } from "./components";
 import { TextField } from "./components/text-field";
-import { GroupStore, GroupStoreMutable } from "./stores/group-store";
+import { GroupStoreMutable } from "./stores/group-store";
 import { GroupContext, GroupContextObject } from "./contexts/group-context";
 import { useForceUpdate } from "./force-update";
 
@@ -84,7 +83,7 @@ interface State {
 class App extends React.Component {
     public state: State = {};
 
-    public componentDidCatch(error: Error, info: ErrorInfo) {
+    public componentDidCatch(error: Error, info: ErrorInfo): void {
         this.setState(() => ({
             error: error,
             info: info