feat: add configuration loader for .env and JSON files

- Add ConfigLoader class for loading RateLimitConfig and GlobalConfig
- Support .env files with FASTAPI_TRAFFIC_* prefixed variables
- Support JSON configuration files with type validation
- Add convenience functions: load_rate_limit_config, load_global_config
- Add load_rate_limit_config_from_env, load_global_config_from_env
- Support custom environment variable prefixes
- Add comprehensive error handling with ConfigurationError
- Add 47 tests for configuration loading
- Add example 11_config_loader.py with 9 usage patterns
- Update examples/README.md with config loader documentation
- Update CHANGELOG.md with new feature
- Fix typo in limiter.py (errant 'fi' on line 4)

fastapi_traffic/core/__init__.py

@@ -1,16 +1,29 @@
 """Core rate limiting components."""
 
 from fastapi_traffic.core.algorithms import Algorithm
-from fastapi_traffic.core.config import RateLimitConfig
+from fastapi_traffic.core.config import GlobalConfig, RateLimitConfig
+from fastapi_traffic.core.config_loader import (
+    ConfigLoader,
+    load_global_config,
+    load_global_config_from_env,
+    load_rate_limit_config,
+    load_rate_limit_config_from_env,
+)
 from fastapi_traffic.core.decorator import rate_limit
 from fastapi_traffic.core.limiter import RateLimiter
 from fastapi_traffic.core.models import RateLimitInfo, RateLimitResult
 
 __all__ = [
     "Algorithm",
+    "ConfigLoader",
+    "GlobalConfig",
     "RateLimitConfig",
-    "rate_limit",
-    "RateLimiter",
     "RateLimitInfo",
     "RateLimitResult",
+    "RateLimiter",
+    "load_global_config",
+    "load_global_config_from_env",
+    "load_rate_limit_config",
+    "load_rate_limit_config_from_env",
+    "rate_limit",
 ]