ClockSettings: Add 'show seconds' toggle to time format settings

Author: https://github.com/cflip
Commit: https://github.com/SerenityOS/serenity/commit/0a92dbd390
Pull-request: https://github.com/SerenityOS/serenity/pull/13647
Reviewed-by: https://github.com/trflynn89

Userland/Applications/ClockSettings/ClockSettingsWidget.gml

@@ -8,7 +8,7 @@
     @GUI::GroupBox {
         title: "Time Format"
         shrink_to_fit: false
-        fixed_height: 160
+        fixed_height: 200
         layout: @GUI::VerticalBoxLayout {
             margins: [16, 8, 8]
         }
@@ -26,14 +26,21 @@
 
             @GUI::RadioButton {
                 name: "24hour_radio"
-                text: "24-hour (12:34:56)"
+                text: "24-hour"
             }
 
             @GUI::RadioButton {
                 name: "12hour_radio"
-                text: "12-hour (12:34 a.m)"
+                text: "12-hour"
             }
 
+            @GUI::CheckBox {
+                name: "seconds_checkbox"
+                text: "Show seconds"
+            }
+
+            @GUI::HorizontalSeparator {}
+
             @GUI::RadioButton {
                 name: "custom_radio"
                 text: "Custom:"