Add description for secure screen setting

app/src/main/res/layout-land/reader_color_filter_sheet.xml

@@ -33,6 +33,7 @@
             android:layout_width="match_parent"
             android:layout_height="wrap_content"
             android:visibility="gone" />
+
     </FrameLayout>
 
     <androidx.core.widget.NestedScrollView

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

@@ -26,6 +26,7 @@
             android:layout_width="match_parent"
             android:layout_height="match_parent"
             android:visibility="gone" />
+
     </FrameLayout>
 
     <androidx.core.widget.NestedScrollView

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

@@ -144,6 +144,7 @@
         <item quantity="other">After %1$s minutes</item>
     </plurals>
     <string name="secure_screen">Secure screen</string>
+    <string name="secure_screen_summary">Hide app contents when switching apps and block screenshots</string>
 
       <!-- Library section -->
     <string name="pref_category_library_display">Display</string>