Allow Rate Limit Distinction Between Instruments

[Lukazoid]

Many of the OKX APIs allow for rate limits to be scoped not only by IP but also by instrument, for example the mark-price endpoint has a rate limit definition of:

Rate Limit: 10 requests per 2 seconds
Rate limit rule: IP + Instrument ID

It would be great if the rate limiting within the OKXRestClient was able to differentiate when different instruments are being requested.