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/common/note-loading-boundary/hooks/use-load-note-from-server.ts

@@ -0,0 +1,28 @@
+/*
+ * SPDX-FileCopyrightText: 2022 The HedgeDoc developers (see AUTHORS file)
+ *
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+import { useAsyncFn } from 'react-use'
+import { getNote } from '../../../../api/notes'
+import { setNoteDataFromServer } from '../../../../redux/note-details/methods'
+import { useSingleStringUrlParameter } from '../../../../hooks/common/use-single-string-url-parameter'
+import type { AsyncState } from 'react-use/lib/useAsyncFn'
+
+/**
+ * Reads the note id from the current URL, requests the note from the backend and writes it into the global application state.
+ *
+ * @return An {@link AsyncState async state} that represents the current state of the loading process.
+ */
+export const useLoadNoteFromServer = (): [AsyncState<void>, () => void] => {
+  const id = useSingleStringUrlParameter('noteId', undefined)
+
+  return useAsyncFn(async () => {
+    if (id === undefined) {
+      throw new Error('Invalid id')
+    }
+    const noteFromServer = await getNote(id)
+    setNoteDataFromServer(noteFromServer)
+  }, [id])
+}