ConfigurableExtension(PreferenceScreen) support (#163)

* initial PreferenceScreen support, works with 'NeoXXX Scans' (pt-br)

* convert EditTextPreference to json successfully

* commit what I've got

* bring back the old SharedPreferences for CustomContext, implement Toast

* put back syer's implementation

AndroidCompat/src/main/java/androidx/preference/PreferenceScreen.java

@@ -1,4 +1,32 @@
 package androidx.preference;
 
-public class PreferenceScreen {
+/*
+ * Copyright (C) Contributors to the Suwayomi project
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+import android.content.Context;
+
+import java.util.LinkedList;
+import java.util.List;
+
+public class PreferenceScreen extends Preference {
+    private List<Preference> preferences = new LinkedList<>();
+
+
+    public PreferenceScreen(Context context) {
+        super(context);
+    }
+
+    public boolean addPreference(Preference preference) {
+        preferences.add(preference);
+
+        return true;
+    }
+
+    public List<Preference> getPreferences(){
+        return preferences;
+    }
 }