Add rejected promises tracking guide to docs

[krystofwoldrich]

Description

Currently the RN Docs only have a small section in the troubleshooting section about issues with promise rejections tracking. (https://docs.sentry.io/platforms/react-native/troubleshooting/#unhandled-promise-rejections)

This issue focuses on creating new page which will describe how rejections are tracked for Hermes, JSC and what are the common issue (moved the the existing troubleshooting page).

Things to include:

• Code snippet on how to enabled/disable
• Note that enabling Hermes rejection tracking will overwrite existing hook (limitation of the engine)
• Note that JSC uses Promise Polyfill (from existing troubleshooting which polyfill is used how it's resolved) and also overwrites existing hook
• Maybe we should also include example of how multiple tools/logging can be use.