feat: Add CMS logo asset to example site

Added the CMS logo from cms-docs-common submodule to the example
site's assets directory so the icon displays in the header dropdown.

Also updated GitHub Actions workflow to copy the icon from the
submodule during build.

Now the "CMS POG Docs" dropdown will display with the CMS logo!

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

Author: andrzejnovak

.github/workflows/deploy-docs.yml

@@ -35,6 +35,11 @@ jobs:
       - name: Install dependencies
         run: pip install -r example/requirements.txt
 
+      - name: Copy assets from submodule
+        run: |
+          mkdir -p example/docs/assets
+          cp example/cms-docs-common/CMSlogo_white_nolabel_1024_May2014.png example/docs/assets/
+
       - name: Build documentation
         run: |
           cd example