feat: add React Native Ease landing page

[NicooleT]

Adds a dedicated React Native Ease landing page to the existing Docusaurus site, with the documentation under /docs. Updates the GitHub banner and app-icon favicon to the new design assets.

• Adds responsive desktop/mobile layouts, installation command copying, documentation links, and feature descriptions.
• Animates the phone illustration in sequence: synchronized React logo/circle entrance, expanding island with a count-up, then a bottom sheet starting alongside the count-up. Mobile waits until half the phone is visible; reduced motion shows the completed state.
• Organizes the page into layout, navigation, hero, footer, and illustration components with a shared CSS module and content file.

Validation: formatting, source ESLint (excluding generated Docusaurus output), library/example/docs TypeScript checks, all 84 Jest tests, and the Docusaurus production build passed. Verified desktop/mobile layouts, animation sequencing, and clipboard interaction in the browser.