manifest: Export MainActivity

* sdk31 requirement

Author: libxzr

app/src/main/AndroidManifest.xml

@@ -10,7 +10,8 @@
         android:theme="@style/Theme.HorizonKernelFlasher">
         <activity
             android:name=".MainActivity"
-            android:screenOrientation="portrait">
+            android:screenOrientation="portrait"
+            android:exported="true">
             <intent-filter>
                 <action android:name="android.intent.action.MAIN" />