No build error displayed when WAI Preview fails to build in PR

[howard-e]

Currently, when the WAI preview fails to build, a message is attached to the top comment of the pull request that reads "WAI Preview Link failed to build on 'Update site files' step".

But with the lack of response due to the workflow dispatch flow currently used between the w3c/aria-practices and w3c/wai-aria-practices, it gives a false impression that the build was successful if one is only checking the build reports at the bottom of the PR. This can be revised.

Recent example