docs: use a propertylist to document shortcode attributes (#732)

exampleSite/content/en/shortcodes/buttons.md

@@ -4,11 +4,20 @@ title: Buttons
 
 Buttons are styled links that can lead to local page or external link.
 
-<!-- prettier-ignore-start -->
+## Usage
+
+<!-- prettier-ignore -->
 ```tpl
 {{</* button relref="/" [class="...", size="large|regular"] */>}}Get Home{{</* /button */>}}
 {{</* button href="https://github.com/thegeeklab/hugo-geekdoc" */>}}Contribute{{</* /button */>}}
 ```
+
+### Attributes
+
+<!-- prettier-ignore-start -->
+<!-- spellchecker-disable -->
+{{< propertylist name=shortcode-buttons sort=name order=asc >}}
+<!-- spellchecker-enable -->
 <!-- prettier-ignore-end -->
 
 ## Example