Add MediaBox divider

reader/src/main/res/layout/view_viewer_edit.xml

@@ -25,10 +25,21 @@
             android:layout_height="wrap_content"
             android:layout_marginLeft="4dp"
             android:layout_marginStart="4dp"
-            app:layout_constraintBottom_toBottomOf="parent"
             app:layout_constraintLeft_toLeftOf="parent"
+            app:layout_constraintRight_toRightOf="@id/view_viewerEdit_divider"
+            app:layout_constraintBottom_toBottomOf="parent"
             app:layout_constraintTop_toTopOf="parent" />
 
+        <View
+            android:id="@+id/view_viewerEdit_divider"
+            android:background="#1e000000"
+            app:layout_constraintLeft_toRightOf="@+id/viewerEdit_tab"
+            app:layout_constraintRight_toLeftOf="@id/viewEdit_layout_tab_content"
+            app:layout_constraintTop_toTopOf="parent"
+            app:layout_constraintBottom_toBottomOf="parent"
+            android:layout_width="1dp"
+            android:layout_height="0dp" />
+
         <android.support.constraint.ConstraintLayout
             android:id="@+id/viewEdit_layout_tab_content"
             android:layout_width="0dp"
@@ -38,7 +49,7 @@
             android:layout_marginTop="12dp"
             android:background="@android:color/darker_gray"
             app:layout_constraintBottom_toBottomOf="parent"
-            app:layout_constraintLeft_toRightOf="@+id/viewerEdit_tab"
+            app:layout_constraintLeft_toRightOf="@+id/view_viewerEdit_divider"
             app:layout_constraintRight_toRightOf="parent"
             app:layout_constraintTop_toTopOf="parent" />