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/__init__.py

@@ -1,30 +1,43 @@
 """FastAPI Traffic - Production-grade rate limiting for FastAPI."""
 
-from fastapi_traffic.core.decorator import rate_limit
-from fastapi_traffic.core.limiter import RateLimiter
-from fastapi_traffic.core.config import RateLimitConfig
-from fastapi_traffic.core.algorithms import Algorithm
 from fastapi_traffic.backends.base import Backend
 from fastapi_traffic.backends.memory import MemoryBackend
 from fastapi_traffic.backends.sqlite import SQLiteBackend
+from fastapi_traffic.core.algorithms import Algorithm
+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.exceptions import (
-    RateLimitExceeded,
     BackendError,
     ConfigurationError,
+    RateLimitExceeded,
 )
 
 __version__ = "0.1.0"
 __all__ = [
-    "rate_limit",
-    "RateLimiter",
-    "RateLimitConfig",
     "Algorithm",
     "Backend",
-    "MemoryBackend",
-    "SQLiteBackend",
-    "RateLimitExceeded",
     "BackendError",
+    "ConfigLoader",
     "ConfigurationError",
+    "GlobalConfig",
+    "MemoryBackend",
+    "RateLimitConfig",
+    "RateLimitExceeded",
+    "RateLimiter",
+    "SQLiteBackend",
+    "load_global_config",
+    "load_global_config_from_env",
+    "load_rate_limit_config",
+    "load_rate_limit_config_from_env",
+    "rate_limit",
 ]
 
 # Optional Redis backend