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/Preference.java

@@ -0,0 +1,68 @@
+package androidx.preference;
+
+/*
+ * 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 com.fasterxml.jackson.annotation.JsonIgnore;
+
+/** A minimal implementation of androidx.preference.Preference */
+public class Preference {
+    // reference: https://android.googlesource.com/platform/frameworks/support/+/996971f962fcd554339a7cb2859cef9ca89dbcb7/preference/preference/src/main/java/androidx/preference/Preference.java
+    // Note: `Preference` doesn't actually hold or persist the value, `OnPreferenceChangeListener` is called and it's up to the extension to persist it.
+
+    @JsonIgnore
+    protected Context context;
+
+    private String key;
+    private CharSequence title;
+    private Object defaultValue;
+
+    @JsonIgnore
+    public OnPreferenceChangeListener onChangeListener;
+
+    public Preference(Context context) {
+        this.context = context;
+    }
+
+    public Context getContext() {
+        return context;
+    }
+
+    public String getKey() {
+        return key;
+    }
+
+    public void setKey(String key) {
+        this.key = key;
+    }
+
+    public void setDefaultValue(Object defaultValue) {
+        this.defaultValue = defaultValue;
+    }
+
+    public CharSequence getTitle() {
+        return title;
+    }
+
+    public void setOnPreferenceChangeListener(OnPreferenceChangeListener onPreferenceChangeListener) {
+        this.onChangeListener = onPreferenceChangeListener;
+    }
+
+    public boolean callChangeListener(Object newValue) {
+        return onChangeListener == null || onChangeListener.onPreferenceChange(this, newValue);
+    }
+
+    public Object getDefaultValue() {
+        return defaultValue;
+    }
+
+    public interface OnPreferenceChangeListener {
+        boolean onPreferenceChange(Preference preference, Object newValue);
+    }
+
+}