docs: add documentation on all shortcodes (#753)

layouts/_shortcodes/filetree/container.html

@@ -1,3 +1,9 @@
+{{- /*
+A file tree container.
+
+@example {{< filetree/container >}}{{< /filetree/container >}}
+*/ -}}
+
 <div class="hextra-filetree hx:mt-6 hx:select-none hx:text-sm hx:text-gray-800 hx:dark:text-gray-300 not-prose">
   <div class="hx:inline-block hx:rounded-lg hx:px-4 hx:py-2 hx:border hx:border-gray-200 hx:dark:border-neutral-800">
     {{- .InnerDeindent -}}

layouts/_shortcodes/filetree/file.html

@@ -1,5 +1,12 @@
-{{- $name := .Get "name" -}}
+{{- /*
+A file in a file tree.
 
+@param {string} name The name of the file.
+
+@example {{< filetree/file name="_index.md" >}}
+*/ -}}
+
+{{- $name := .Get "name" -}}
 
 <li class="hx:flex hx:list-none">
   <span class="hx:inline-flex hx:cursor-default hx:items-center hx:py-1">

layouts/_shortcodes/filetree/folder.html

@@ -1,3 +1,12 @@
+{{- /*
+A folder in a file tree.
+
+@param {string} name The name of the folder.
+@param {string} state The state of the folder.
+
+@example {{< filetree/folder name="docs" state="closed" >}}
+*/ -}}
+
 {{- $name := .Get "name" -}}
 {{- $state := .Get "state" | default "open" }}