fix: correct FORD page_dir configuration syntax for examples processing

Fixes FORD configuration syntax to properly process doc/examples/ directory:
- Changed page_dir from multi-line to single-line format
- Now generates all 17 example HTML pages with embedded image references
- Restores working Examples Gallery navigation in FORD documentation
- Image paths preserved: ../../media/examples/example_name/output.png

Verified: All example pages now generated correctly in build/doc/page/examples/
with proper embedded image references for GitHub Pages deployment.

Generated with [Claude Code](https://claude.ai/code)

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

Author: krystophny

doc.md

@@ -7,8 +7,7 @@ project_github: https://github.com/krystophny/fortplotlib
 project_download: https://github.com/krystophny/fortplotlib/releases
 output_dir: ./build/doc
 media_dir: ./doc/media
-page_dir: ./doc
-          ./doc/examples
+page_dir: ./doc ./doc/examples
 src_dir: ./src
          ./example
 exclude_dir: ./thirdparty