fix: Move content into to frontend directory

Doing this BEFORE the merge prevents a lot of merge conflicts.

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

frontend/src/components/editor-page/app-bar/read-only-mode-button.tsx

@@ -0,0 +1,34 @@
+/*
+ * SPDX-FileCopyrightText: 2021 The HedgeDoc developers (see AUTHORS file)
+ *
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+import React from 'react'
+import { Button } from 'react-bootstrap'
+import { ForkAwesomeIcon } from '../../common/fork-awesome/fork-awesome-icon'
+import { useTranslation } from 'react-i18next'
+import { useApplicationState } from '../../../hooks/common/use-application-state'
+import Link from 'next/link'
+
+/**
+ * Button that links to the read-only version of a note.
+ */
+export const ReadOnlyModeButton: React.FC = () => {
+  const { t } = useTranslation()
+  const noteIdentifier = useApplicationState((state) => state.noteDetails.primaryAddress)
+
+  return (
+    <Link href={`/s/${noteIdentifier}`}>
+      <a target='_blank'>
+        <Button
+          title={t('editor.documentBar.readOnlyMode') ?? undefined}
+          className='ms-2 text-secondary'
+          size='sm'
+          variant='outline-light'>
+          <ForkAwesomeIcon icon='file-text-o' />
+        </Button>
+      </a>
+    </Link>
+  )
+}