feat: Make game sub

- Move game and intro to own collection
- Add index
- Add brand placeholder to shortcodes
- Add variant of placeholder to menu

source/screens/demo/examples/game/menu.liquid

@@ -0,0 +1,29 @@
+---
+title: Menu
+tags:
+- game
+---
+{% assign bodyClass = 'body_game' -%}
+{% layout 'hippie/simple.liquid' %}
+
+{% block body %}
+<div class="sec_main_center">
+	<nav role="doc-toc">
+		<hgroup>
+			<h1>Game - TFW</h1>
+			<p>Additional name</p>
+		</hgroup>
+		<ul class="link">
+			<li><a href="#new">Neues Spiel</a></li>
+			<li><a href="#continue">Spiel fortsetzen</a></li>
+			<li><a href="#options">Einstellungen</a></li>
+			<li><a href="#quit">Spiel beenden</a></li>
+		</ul>
+	</nav>
+</div>
+<footer>
+	{% brand 'brand', 'last' %}
+	<p>Marke</p>
+	{% endbrand %}
+</footer>
+{% endblock %}