For #17963 - Present Fenix as a browser app to the system

Fenix will now be able to be started from a call to
Intent.makeMainSelectorActivity(Intent.ACTION_MAIN, Intent.CATEGORY_APP_BROWSER)

For more info:
https://developer.android.com/reference/android/content/Intent#CATEGORY_APP_BROWSER

app/src/main/AndroidManifest.xml

@@ -145,6 +145,15 @@
             android:exported="true"
             android:excludeFromRecents="true" >
 
+            <!--
+              Respond to `Intent.makeMainSelectorActivity(Intent.ACTION_MAIN, Intent.CATEGORY_APP_BROWSER)`
+            -->
+            <intent-filter>
+                <action android:name="android.intent.action.MAIN" />
+                <category android:name="android.intent.category.APP_BROWSER"/>
+                <category android:name="android.intent.category.DEFAULT"/>
+            </intent-filter>
+
             <intent-filter>
                 <action android:name="android.intent.action.VIEW" />