[ci] update codeowners (#6542)

.github/CODEOWNERS

@@ -7,4 +7,4 @@
 # offer a reasonable automatic best-guess
 
 # catch-all rule (this only gets matched if no rules below match)
-*    @guolinke @jameslamb @shiyu1994 @jmoralez @borchero
+*    @guolinke @jameslamb @shiyu1994 @jmoralez @borchero @StrikerRUS