Client-side exception autocapture rate limiting added

Minor changes

• b9f3208 Add opt-in client-side rate limiting for exception autocapture, using the same token bucket algorithm as the posthog-js and posthog-node SDKs: a bucket per exception type allows a burst of captures, then refills over time. Rate-limited exceptions are skipped before they reach the ingestion queue. Disabled by default; enable with the new enable_exception_autocapture_rate_limiting client option and tune via exception_autocapture_bucket_size (default 50), exception_autocapture_refill_rate (default 10), and exception_autocapture_refill_interval_seconds (default 10). — Thanks @hpouillot!