Function global 

pub fn global() -> &'static RateLimiter

Return the process-wide rate limiter, initialized from environment variables.

Variable	Default	Meaning
RWS_CONFIG_RATE_LIMIT_MAX_REQUESTS	1000	Requests allowed per window
RWS_CONFIG_RATE_LIMIT_WINDOW_SECS	60	Window length in seconds

Returns None when rate limiting is disabled (RWS_CONFIG_RATE_LIMIT_MAX_REQUESTS=0).