Add vertical viewer. Allow to select a viewer

app/src/main/res/layout/viewer_verticalviewpager.xml

@@ -0,0 +1,8 @@
+<?xml version="1.0" encoding="utf-8"?>
+<fr.castorflex.android.verticalviewpager.VerticalViewPager
+    xmlns:android="http://schemas.android.com/apk/res/android"
+    android:id="@+id/view_pager"
+    android:layout_width="match_parent"
+    android:layout_height="match_parent">
+
+</fr.castorflex.android.verticalviewpager.VerticalViewPager>

app/src/main/res/values/arrays.xml

@@ -0,0 +1,17 @@
+<?xml version="1.0" encoding="utf-8"?>
+<resources>
+    <string-array name="viewers">
+        <item>@string/left_to_right_viewer</item>
+        <item>@string/right_to_left_viewer</item>
+        <item>@string/vertical_viewer</item>
+        <item>@string/webtoon_viewer</item>
+    </string-array>
+
+    <string-array name="viewers_values">
+        <item>1</item>
+        <item>2</item>
+        <item>3</item>
+        <item>4</item>
+    </string-array>
+
+</resources>

app/src/main/res/values/strings.xml

@@ -49,5 +49,10 @@
     <string name="title_activity_settings">Settings</string>
     <string name="pref_hide_status_bar">Hide status bar</string>
     <string name="pref_hide_status_bar_summary">This option will hide the status bar while reading</string>
+    <string name="pref_viewer_type">Default viewer</string>
+    <string name="left_to_right_viewer">Left to right</string>
+    <string name="right_to_left_viewer">Right to left</string>
+    <string name="vertical_viewer">Vertical</string>
+    <string name="webtoon_viewer">Webtoon (experimental)</string>
 
 </resources>

app/src/main/res/xml/preferences.xml

@@ -6,4 +6,10 @@
         android:summary="@string/pref_hide_status_bar_summary"
         android:key="hide_status_bar" />
 
+    <ListPreference android:title="@string/pref_viewer_type"
+        android:key="default_viewer"
+        android:entries="@array/viewers"
+        android:entryValues="@array/viewers_values"
+        android:defaultValue="1"/>
+
 </PreferenceScreen>