feat(frontend): add isOwner hook

This hook is used to determine if the current user is the owner of the note

Signed-off-by: Philip Molares <philip.molares@udo.edu>

frontend/src/hooks/common/use-is-owner.ts

@@ -0,0 +1,19 @@
+/*
+ * SPDX-FileCopyrightText: 2023 The HedgeDoc developers (see AUTHORS file)
+ *
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+import { useApplicationState } from './use-application-state'
+import { useMemo } from 'react'
+
+/**
+ * Determines if the current user is the owner of the current note.
+ *
+ * @return True, if the current user is owner.
+ */
+export const useIsOwner = (): boolean => {
+  const owner = useApplicationState((state) => state.noteDetails.permissions.owner)
+  const me: string | undefined = useApplicationState((state) => state.user?.username)
+
+  return useMemo(() => !!me && owner === me, [owner, me])
+}