fix: Add build script and fix manifest

- Add build-apk.sh for easy compilation
- Simplify AndroidManifest.xml
- Fix themes.xml to use basic Android themes
- Enable BuildConfig
- Add okhttp-dnsoverhttps dependency

android-sdk/platforms/android-34/templates/java_file.template

@@ -0,0 +1,15 @@
+package PACKAGE;
+
+import android.app.Activity;
+import android.os.Bundle;
+
+public class ACTIVITY_CLASS_NAME extends Activity
+{
+    /** Called when the activity is first created. */
+    @Override
+    public void onCreate(Bundle savedInstanceState)
+    {
+        super.onCreate(savedInstanceState);
+        setContentView(R.layout.main);
+    }
+}