Add details shortcode (#370)

Author: jarrodmillman

layouts/shortcodes/details.html

@@ -0,0 +1,21 @@
+{{/*
+
+doc: Hide the details.
+
+{{< details "**Sunday**" >}}
+| Time | Description |
+|------|-------------|
+| | Arrive |
+| | Dinner (self organized) |
+{{< /details >}}
+
+*/}}
+
+{{ $summary:= .Get 0 | markdownify }}
+{{ $content := .Inner | markdownify }}
+<p>
+  <details>
+      <summary>{{$summary}}</summary>
+      <p>{{$content}}</p>
+  </details>
+</p>