These files control what users see when they visit https://vuln.go.dev, and when they get a 404 on that site.
After these files are modified and the CL has been submitted, copy them to the vuln DB bucket:
gsutil cp index.html 404.html gs://go-vulndb
The go-vulndb bucket must be configured to display these pages. That can be done with
gsutil web set -m index.html -e 404.html gs://go-vulndb
Use gsutil web get gs://go-vulndb to display the configuration.