doc: document required proguard rules

android/README.md

    `"file:${rootProject.projectDir}/../../../jitsi/jitsi-maven-repository/releases"`
    in android/build.gradle for the third-party react-native modules which Jitsi
    Meet SDK for Android depends on and are not publicly available in Maven
-   repositories. Generally, if you are modifying the JavaSource code of Jitsi
+   repositories. Generally, if you are modifying the JavaScript code of Jitsi
    Meet SDK for Android only, you will very likely need to consider the former
    only.
 
 
 The `data` `Map` contains an "error" key with the error and a "url" key with the
 conference URL which necessitated the loading of the configuration file.
+
+## ProGuard rules
+
+When using the SDK on a project some proguard rules have to be added in order
+to avoid necessary code being stripped. Add the following to your project's
+rules file:
+
+```
+# React Native
+
+# Keep our interfaces so they can be used by other ProGuard rules.
+# See http://sourceforge.net/p/proguard/bugs/466/
+-keep,allowobfuscation @interface com.facebook.proguard.annotations.DoNotStrip
+-keep,allowobfuscation @interface com.facebook.proguard.annotations.KeepGettersAndSetters
+-keep,allowobfuscation @interface com.facebook.common.internal.DoNotStrip
+
+# Do not strip any method/class that is annotated with @DoNotStrip
+-keep @com.facebook.proguard.annotations.DoNotStrip class *
+-keep @com.facebook.common.internal.DoNotStrip class *
+-keepclassmembers class * {
+    @com.facebook.proguard.annotations.DoNotStrip *;
+    @com.facebook.common.internal.DoNotStrip *;
+}
+
+-keepclassmembers @com.facebook.proguard.annotations.KeepGettersAndSetters class * {
+  void set*(***);
+  *** get*();
+}
+
+-keep class * extends com.facebook.react.bridge.JavaScriptModule { *; }
+-keep class * extends com.facebook.react.bridge.NativeModule { *; }
+-keepclassmembers,includedescriptorclasses class * { native <methods>; }
+-keepclassmembers class *  { @com.facebook.react.uimanager.UIProp <fields>; }
+-keepclassmembers class *  { @com.facebook.react.uimanager.annotations.ReactProp <methods>; }
+-keepclassmembers class *  { @com.facebook.react.uimanager.annotations.ReactPropGroup <methods>; }
+
+-dontwarn com.facebook.react.**
+
+# TextLayoutBuilder uses a non-public Android constructor within StaticLayout.
+# See libs/proxy/src/main/java/com/facebook/fbui/textlayoutbuilder/proxy for details.
+-dontwarn android.text.StaticLayout
+
+# okhttp
+
+-keepattributes Signature
+-keepattributes *Annotation*
+-keep class okhttp3.** { *; }
+-keep interface okhttp3.** { *; }
+-dontwarn okhttp3.**
+
+# okio
+
+-keep class sun.misc.Unsafe { *; }
+-dontwarn java.nio.file.*
+-dontwarn org.codehaus.mojo.animal_sniffer.IgnoreJRERequirement
+-dontwarn okio.**
+
+# WebRTC
+
+-keep class org.webrtc.** { *; }
+
+# Jisti Meet SDK
+
+-keep class org.jitsi.meet.sdk.** { *; }
+```
+