Make changes to reduce the release APK/app bundle size.

app/build.gradle

@@ -22,7 +22,7 @@ android {
 
     buildTypes {
         release {
-            minifyEnabled false
+            minifyEnabled true
             proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
         }
     }

app/proguard-rules.pro

@@ -18,4 +18,8 @@
 
 # If you keep the line number information, uncomment this to
 # hide the original source file name.
-#-renamesourcefileattribute SourceFile
+#-renamesourcefileattribute SourceFile
+# For the Secp256k1 library
+-keep class fr.acinq.secp256k1.jni.** { *; }
+# For the NostrPostr library
+-keep class nostr.postr.** { *; }