replace slippers with django-cotton

main reason: slippers cannot pass request via context inside its
components, making it annoying to use template takes that take request.
more reasons: not actively worked on, no named slots, having to define
components in components.yaml + new components do not get registered
without restarting server

games/templates/cotton/gamelink.html

@@ -0,0 +1,10 @@
+<span class="truncate-container">
+    <a class="underline decoration-slate-500 sm:decoration-2"
+       href="{% url 'view_game' game_id %}">
+        {% if slot %}
+            {{ slot }}
+        {% else %}
+            {{ name }}
+        {% endif %}
+    </a>
+</span>