Try to manually build it with strict.

.github/workflows/ci.yml

@@ -13,7 +13,7 @@ jobs:
         run: sudo gem install mdl
       - name: Lint markdown files
         run: mdl . -r ~MD036,~MD024,~MD004,~MD029
-      - name: Try build docs
-        uses: jnanadarshan/mkdocs-build-action@v0.24
+      - run: pip install -r requirements.txt
+      - run: mkdocs build --strict
         # Suppress 036 Emphasis used instead of a header
         # Suppress 024 Multiple headers with the same content