Fix surge previews on pull requests

[jaydrogers]

What this PR attempts to fix

https://github.com/postalserver/docs/issues/14

[github-actions[bot]]

🎊 PR Preview b4797d68dd52980a68ef3c6e57f09d356c6a07f1 has been successfully built and deployed to https://postalserver-docs-preview-pr-37.surge.sh

:clock1: Build time: 59.952s

_{🤖 By surge-preview}