Update README.md for v1.3.0 with rate limiting documentation

Rewrite README to accurately reflect the v1.3.0 API: correct constructor
signature, rate limiting & throttling section, SlidingWindowRateLimiter,
SharpApiError, adaptive polling, SubscriptionInfo new fields, and updated
package structure. Remove references to deprecated sharpapi-node-client.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: makowskid