Become a CODEOWNER for typing (#31374)

Author: JelleZijlstra

.github/CODEOWNERS

@@ -136,7 +136,7 @@ Lib/ast.py                    @isidentical
 
 **/*idlelib*                  @terryjreedy
 
-**/*typing*                   @gvanrossum @Fidget-Spinner
+**/*typing*                   @gvanrossum @Fidget-Spinner @JelleZijlstra
 
 **/*asyncore                  @giampaolo
 **/*asynchat                  @giampaolo