docs: Add Android release build troubleshooting section

[BSchindeleAnother]

This PR adds up documentation to set up the necessary proguard exception for release builds to work on android, as proposed in #76.

[niclasEX]

@BSchindeleAnother
What are your thoughts on #133 #129
Is there a reason not to do it with consumer rules?

[niclasEX]

If this is to be added to the documentation it might make sense to also include documentation for kotlin:

buildTypes {
    release {
        {... existing lines ...}
        isMinifyEnabled = true
        isShrinkResources = true
        proguardFiles(
            getDefaultProguardFile("proguard-android-optimize.txt"),
            "proguard-rules.pro"
        )
    }
}