add nav tree

src/lib/components/nav-item.svelte

@@ -0,0 +1,13 @@
+<li><slot /></li>
+
+<style lang="less">
+  li {
+    margin: 0;
+    padding: @padding-md;
+    text-align: center;
+  }
+
+  li:not(:last-of-type) {
+    border-bottom: 1px solid @color-dark;
+  }
+</style>

src/lib/components/nav-tree.svelte

@@ -0,0 +1,14 @@
+<nav>
+  <ul>
+    <slot />
+  </ul>
+</nav>
+
+<style lang="less">
+  ul {
+    border-bottom: 2px solid @color-dark;
+    list-style-type: none;
+    margin: 0;
+    padding: 0;
+  }
+</style>