GamesSettings: Introduce a new GamesSettings application :^)

This currently has exactly one setting: The background colour for card
games. My thinking is, it's better to not have a Settings application
for each individual game we include in the system, since most will only
have a small number of settings, all Settings windows have tabs anyway,
and I don't want to flood the Settings app list unnecessarily.

As for having a single setting for all the card games: it's nice when
things match. :^)

Userland/Applications/GamesSettings/CardSettingsWidget.gml

@@ -0,0 +1,19 @@
+@GUI::Frame {
+    fill_with_background_color: true
+    layout: @GUI::VerticalBoxLayout {
+        margins: [8]
+    }
+
+    @GUI::GroupBox {
+        title: "Background Color"
+        max_height: "shrink"
+        layout: @GUI::VerticalBoxLayout {
+            margins: [8]
+        }
+
+        @GUI::ColorInput {
+            name: "cards_background_color"
+            has_alpha_channel: false
+        }
+    }
+}