Add GitHub Pages GIF gallery

[rsasaki0109]

Goal

Create a lightweight project page that makes the best loops visible without asking visitors to scroll through the full README.

Tasks

• Choose the strongest 8 to 12 GIFs from the existing generated assets.
• Build a simple GitHub Pages page with a short intro, first-run command, and category sections.
• Link the page from the repository homepage once Pages is enabled.
• Keep the page generated from existing assets, not separate animations.

Acceptance Criteria

• GitHub Pages is enabled for the repository.
• The page shows the project promise, install command, and selected GIFs.
• The page links back to the README and examples index.