Introduce experimental OpenAPI shortcode

exampleSite/content.en/docs/content/shortcodes/experimental/_index.md

@@ -0,0 +1,3 @@
+---
+bookCollapseSection: true
+---

exampleSite/content.en/docs/content/shortcodes/experimental/cards.md

@@ -1,6 +1,6 @@
 # Cards
 
-Content blocks with optional images and links. Often used with [Columns](/docs/content/shortcodes/columns) for grid layouts.
+Content blocks with optional images and links. Often used with [Columns](/docs/content/shortcodes/columns/) for grid layouts.
 
 ## Syntax
 
@@ -18,7 +18,7 @@ Markdown content
   Cards can display an image above the content.
   {{< /card >}}
 
-- {{< card href="/docs/content/shortcodes/cards" >}}
+- {{< card href="/docs/content/shortcodes/experimental/cards/" >}}
   ### With Link {anchor=false}
   When `href` is set, the entire card becomes clickable.
   {{< /card >}}

exampleSite/content.en/docs/content/shortcodes/experimental/openapi.md

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+---
+title: OpenAPI
+---
+
+# OpenAPI
+
+Renders an OpenAPI 3.x specification as a documentation page. Operations are grouped by their first tag.
+
+## Syntax
+
+```tpl
+{{%/* openapi src="spec.json" */%}}
+```
+
+The spec file is loaded via `resources.Get`, so the path is relative to the site's `assets/` directory. JSON and YAML are both supported.
+
+## Example
+
+{{% openapi src="tictactoe.json" %}}