Add docs for PreviewServerParams.open used by adapters (#14238)

Co-authored-by: Yan <61414485+yanthomasdev@users.noreply.github.com>

Author: ArmandPhilippot

src/content/docs/en/reference/adapter-reference.mdx

@@ -1181,6 +1181,16 @@ Describes the [configured HTTP response headers](/en/reference/configuration-ref
 
 Describes the [configured allowed hosts](/en/reference/configuration-reference/#serverallowedhosts) that the preview server should respond to.
 
+#### `PreviewServerParams.open`
+
+<p>
+
+**Type:** `string | boolean`<br />
+<Since v="7.0.8" />
+</p>
+
+Specifies the [configured open option](/en/reference/configuration-reference/#serveropen) for the preview server.
+
 #### `PreviewServerParams.root`
 
 <p>