Added main menu which is currently not yet functional

lib/states/main_menu.rb

@@ -0,0 +1,23 @@
+class MainMenu < CyberarmEngine::Container
+  def setup
+    show_cursor = true
+    set_layout_y(10, 20)
+
+    flow(width: $window.width, padding: 10, margin: 10) do
+      image("assets/logo_small.png")
+      text "Main Menu", align: "center", size: 30
+    end
+
+    stack(width: 250) do
+      button("Play")
+      button("About")
+      button("Exit") do
+        close
+      end
+    end
+  end
+
+  def draw
+    fill(Gosu::Color.new(0xff7a0d71))
+  end
+end