Get the nethack page looking good again

Update all the CSS classes and fix the layout so it looks good in the new theme.
Convert a bunch of CSS classes to BEM style.

layouts/nethack/single.html

@@ -0,0 +1,28 @@
+{{ define "main" }}
+  <main class="main--single  main--nethack">
+    {{ if .Title -}}
+      <header class="page-header">
+        {{ partial "page_header.html" (dict "page" .) }}
+      </header>
+    {{ end }}
+
+    {{- .Content -}}
+
+    <footer class="page-footer">
+      {{ partial "page/footer.html" . }}
+    </footer>
+  </main>
+  <div id="dungeon-background"></div>
+{{ end }}
+
+{{ define "after_js" }}
+  {{/* TODO: Get the dungon script working again. :( */}}
+  {{/*
+  {{ with resources.Get "scripts/lib/p5-1.5.0.js" }}
+    <script defer src="{{ .Permalink }}"></script>
+  {{ end }}
+  {{ with resources.Get "scripts/nethack/dungeon.js" }}
+    <script defer src="{{ .Permalink }}"></script>
+  {{ end }}
+  */}}
+{{ end }}