Update CODEOWNERS (#336)

Author: markmcd

CODEOWNERS

@@ -7,6 +7,7 @@
 # demos/palm/web/quick-prompt
 # demos/palm/web/textfx
 examples/gemini/python/docs-agent @nickvander @rundong08 @Meggin @kyolee415
+examples/gemini/node/flutter_theme_agent/ @khanhnwin @joefernandez
 demos/palm/node/pipet-code-agent @joefernandez @shilpakancharla @markmcd
 
 site/ @google/generative-ai-site-team