feat: add 7 built-in middleware components inspired by Hono.js

New Middleware:
- CORS: Cross-Origin Resource Sharing with full configuration support
- Cookie Helper: Cookie management with signed cookie support (HMAC-SHA256)
- JWT: JSON Web Token authentication (HS256/384/512)
- Bearer Auth: Simple Bearer token authentication
- Compression: Gzip and deflate response compression
- Rate Limiting: Request rate limiting with customizable stores
- Validator: Schema-based request validation

Features:
- Context store for middleware data sharing (get/set/get_client_ip)
- Middleware export module with utility functions
- Comprehensive property-based tests for all middleware
- Example file demonstrating all middleware usage

Files Added:
- cors.v, cookie.v, jwt.v, bearer_auth.v, compress.v, rate_limit.v, validator.v
- middleware.v (unified exports)
- examples/middleware_demo.v
- tests/test_*.v (9 new test files)

Documentation:
- Updated README.md with detailed middleware usage guide
- Added Schema Builder API documentation

v.mod

@@ -1,7 +1,7 @@
 Module {
 	name: 'hono'
 	description: 'A high-performance V language web framework inspired by Hono.js, featuring hybrid routing, LRU cache, middleware support, and more.'
-	version: '0.4.0'
+	version: '0.5.0'
 	license: 'MIT'
 	dependencies: []
 }