Fail on warnings.

Author: jyasskin

.github/workflows/deploy.yml

@@ -14,5 +14,5 @@ jobs:
     - uses: actions/checkout@v4
     - uses: w3c/spec-prod@v2
       with:
-        BUILD_FAIL_ON: fatal
+        BUILD_FAIL_ON: warning
         GH_PAGES_BRANCH: gh-pages