feat: add flutter-dev skill

Add comprehensive Flutter cross-platform development guide covering:
- Widget patterns and const optimization
- Riverpod/Bloc state management
- GoRouter navigation
- Performance optimization
- Testing strategies
- Platform-specific implementations

Made-with: Cursor

README.md

@@ -14,6 +14,7 @@ Development skills for AI coding agents. Plug into your favorite AI coding tool
 | `fullstack-dev` | Full-stack backend architecture and frontend-backend integration. REST API design, auth flows (JWT, session, OAuth), real-time features (SSE, WebSocket), database integration (SQL / NoSQL), production hardening, and release checklist. Guided workflow: requirements → architecture → implementation. | Official |
 | `android-native-dev` | Android native application development with Material Design 3. Kotlin / Jetpack Compose, adaptive layouts, Gradle configuration, accessibility (WCAG), build troubleshooting, performance optimization, and motion system. | Official |
 | `ios-application-dev` | iOS application development guide covering UIKit, SnapKit, and SwiftUI. Touch targets, safe areas, navigation patterns, Dynamic Type, Dark Mode, accessibility, collection views, and Apple HIG compliance. | Official |
+| `flutter-dev` | Flutter cross-platform development covering widget patterns, Riverpod/Bloc state management, GoRouter navigation, performance optimization, and testing strategies. | Official |
 | `shader-dev` | Comprehensive GLSL shader techniques for creating stunning visual effects — ray marching, SDF modeling, fluid simulation, particle systems, procedural generation, lighting, post-processing, and more. ShaderToy-compatible. | Official |
 | `gif-sticker-maker` | Convert photos (people, pets, objects, logos) into 4 animated GIF stickers with captions. Funko Pop / Pop Mart style, powered by MiniMax Image & Video Generation API. | Official |
 | `minimax-pdf` | Generate, fill, and reformat PDF documents with a token-based design system. CREATE polished PDFs from scratch (15 cover styles), FILL existing form fields, or REFORMAT documents into a new design. Print-ready output with typography and color derived from document type. | Official |