Add spacing for content in panel

Added the `space-y-2` class to keep all the content inside panels evenly
spaced.

layouts/shortcodes/inPanel.html

@@ -1,3 +1,3 @@
-<div class="panel my-2">
+<div class="panel my-2 space-y-2">
     {{ .Inner | markdownify }}
 </div>