Document variant support for Sentry Android Gradle Plugin

[marandaneto]

Core or SDK?

Platform/SDK

Which part? Which one?

sentry android gradle plugin

Description

Document variant support implemented by getsentry/sentry-android-gradle-plugin#140

Suggested Solution

Document examples on how to use it in the gradle plugin page https://docs.sentry.io/platforms/android/proguard/#gradle-configuration -> https://github.com/getsentry/sentry-docs/edit/master/src/platforms/android/common/proguard.mdx

[marandaneto]

cc @cortinico in case you fancy it :) otherwise, I can do it once I am back from vacay late this month

[cortinico]

I'm quite full at the moment, but I'll keep this in the inbox :) Maybe I find some spare time

[cortinico]

Here you go :) #3991