Moved theme into its own file, added message dialog state to show error messages, game install button is disabled when clicked and if there is an installer task pending or running

lib/states/message_dialog.rb

@@ -0,0 +1,35 @@
+class W3DHub
+  class States
+    class MessageDialog < CyberarmEngine::GuiState
+      def setup
+        window.show_cursor = true
+
+        theme(W3DHub::THEME)
+
+        background 0xee_444444
+
+        stack(width: 1.0, height: 1.0, margin: 128, padding: 8, background: 0xee_222222) do
+          flow(width: 1.0, height: 0.06) do
+            image "#{GAME_ROOT_PATH}/media/ui_icons/warning.png", width: 0.04, align: :center, color: 0xff_ff8800
+
+            tagline "<b>#{@options[:title]}</b>", width: 0.9, text_align: :center
+          end
+
+          para @options[:message], width: 1.0, height: 0.7, padding: 8
+
+          button "Okay", width: 1.0, margin_top: 64 do
+            pop_state
+          end
+        end
+      end
+
+      def draw
+        previous_state&.draw
+
+        Gosu.flush
+
+        super
+      end
+    end
+  end
+end