Add Cloudflare RateLimit component

[declanlscott]

Adds sst.cloudflare.RateLimit component using the rate limit binding for simple rate limiting in Cloudflare Workers.

// sst.config.ts
const rateLimit = new sst.cloudflare.RateLimit("MyRateLimit", {
  namespaceId: 1001,
  limit: 100,
  period: "1 minute",
});

This requires @pulumi/cloudflare minimum v6.15.0 from #6852.