Separate stub Magisk Manager to a module

stub/src/main/java/com/topjohnwu/magisk/BootLauncher.java

@@ -0,0 +1,16 @@
+package com.topjohnwu.magisk;
+
+import android.content.BroadcastReceiver;
+import android.content.Context;
+import android.content.Intent;
+import android.text.TextUtils;
+
+public class BootLauncher extends BroadcastReceiver {
+    @Override
+    public void onReceive(Context context, Intent intent) {
+        if (TextUtils.equals(intent.getAction(), Intent.ACTION_BOOT_COMPLETED)) {
+            Intent i = new Intent(context, MainActivity.class).addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
+            context.startActivity(i);
+        }
+    }
+}