index for sub pages

src/sass/app.scss

@@ -125,3 +125,35 @@
     transform: rotateX(180deg);
   }
 }
+
+.page-nav {
+  ol {
+    padding: 0;
+    list-style: none;
+    counter-reset: item;
+    font-size: 1rem;
+  }
+  ol li {
+      display: block;
+      padding-left: 2em;
+  }
+  ol li:before {
+      display: inline-block;
+      margin-left: -2em;
+      margin-right: .5em;
+      text-align: center;
+      content: counters(item, ".") ".";
+      counter-increment: item;
+  }
+  ol ol {
+      width: auto;
+      margin: 0;
+      padding: .5em 0;
+  }
+  ol li li:before {
+      content: counters(item, ".") " ";
+  }
+  ol ol ol {
+      padding: .5em 0 0;
+  }
+}