Games: Add Spider

Scoring is designed to mimic Microsoft's implementation - starting at
500, decreasing by 1 every move, and increasing by 100 for every full
stack.

Fixes GH-5319.

Userland/Games/Spider/Spider.gml

@@ -0,0 +1,17 @@
+@GUI::Widget {
+    fill_with_background_color: true
+
+    layout: @GUI::VerticalBoxLayout {
+    }
+
+    @Spider::Game {
+        name: "game"
+        fill_with_background_color: true
+        background_color: "green"
+    }
+
+    @GUI::Statusbar {
+        name: "statusbar"
+        label_count: 3
+    }
+}