Switch the base framework from Create React App to Next.JS

Signed-off-by: Tilman Vatteroth <git@tilmanvatteroth.de>

src/pages/_app.tsx

@@ -0,0 +1,31 @@
+/*
+ SPDX-FileCopyrightText: 2021 The HedgeDoc developers (see AUTHORS file)
+
+ SPDX-License-Identifier: AGPL-3.0-only
+ */
+import type { AppProps } from 'next/app'
+import { store } from '../redux'
+import { Provider } from 'react-redux'
+import { ErrorBoundary } from '../components/error-boundary/error-boundary'
+import { ApplicationLoader } from '../components/application-loader/application-loader'
+import '../../global-styles/dark.scss'
+import '../../global-styles/index.scss'
+import type { NextPage } from 'next'
+
+/**
+ * The actual hedgedoc next js app.
+ * Provides necessary wrapper components to every page.
+ */
+const HedgeDocApp: NextPage<AppProps> = ({ Component, pageProps }: AppProps) => {
+  return (
+    <Provider store={store}>
+      <ApplicationLoader>
+        <ErrorBoundary>
+          <Component {...pageProps} />
+        </ErrorBoundary>
+      </ApplicationLoader>
+    </Provider>
+  )
+}
+
+export default HedgeDocApp