Add website button lint check (#39)

Once cl/534605271 is submitted & sync'd, we can turn this check back on.

Author: markmcd

.github/workflows/notebooks.yml

@@ -66,6 +66,5 @@ jobs:
             --styles=google,tensorflow \
             --arg=repo:google/generative-ai-docs --arg=branch:main \
             --exclude_lint=tensorflow::button_download \
-            --exclude_lint=tensorflow::button_website \
             "${changed_notebooks[@]}"
         fi