v4.2.5: automatically dedupe subscribe requests

What's Changed

• fix(v4.2.5, #477): automatically dedupe topic requests if already subscribed by @tiagosiebler in #478

This provides convenience in calling the subscribe method, where it will only emit subscribe events to bybit for the topics that haven't been subscribed to yet, preventing the scenario in #477 (which will cause non-duplicate topic subs to fail)

Full Changelog: v4.2.4...v4.2.5