enh: add codeowner

Signed-off-by: Christopher Ng <chrng8@gmail.com>
(cherry picked from commit 113d061919)

.github/CODEOWNERS

@@ -11,6 +11,7 @@
 /apps/federation/appinfo/info.xml             @datenangebot
 /apps/files/appinfo/info.xml                  @skjnldsv @Pytal @ArtificialOwl @come-nc @artonge @icewind1991 @szaimen @susnux @Fenn-CS
 /apps/files_external/appinfo/info.xml         @icewind1991 @artonge
+/apps/files_reminders/appinfo/info.xml        @Pytal
 /apps/files_sharing/appinfo/info.xml          @skjnldsv @come-nc
 /apps/files_trashbin/appinfo/info.xml         @Pytal @icewind1991
 /apps/files_versions/appinfo/info.xml         @artonge @icewind1991