Add sillyguodong to maintainers (#23067)

[List of mine merged
PR](https://github.com/go-gitea/gitea/pulls?q=is%3Apr+author%3Asillyguodong+is%3Amerged+)

MAINTAINERS

@@ -49,3 +49,4 @@ Jason Song <i@wolfogre.com> (@wolfogre)
 Yarden Shoham <hrsi88@gmail.com> (@yardenshoham)
 Yu Tian <zettat123@gmail.com> (@Zettat123)
 Eddie Yang <576951401@qq.com> (@yp05327)
+Dong Ge <gedong_1994@163.com> (@sillyguodong)