Document how to use Sentry with Proguard in JVM

### SDK

Java SDK

### Description

We should add a section describing how to use proguard with Sentry on the JVM. I.e. describe which proguard rules need to be added for Sentry to work.

Relates to: https://github.com/getsentry/sentry-java/issues/3340

### Suggested Solution

_No response_