docs: add x-oai-deviceAuthorization extension page

registries/_extension/x-oai-deviceAuthorization.md

@@ -0,0 +1,44 @@
+---
+owner: baywet
+issue:
+description: A device authorization OAuth2 flow, used when targeting OpenAPI versions prior to 3.2.
+schema:
+  type: object
+objects: [ "OAuth Flows Object" ]
+layout: default
+---
+
+{% capture summary %}
+OpenAPI 3.2 introduced the `deviceAuthorization` field on OAuth Flows Objects to define a device authorization OAuth2 flow.
+
+The `x-oai-deviceAuthorization` extension brings this same capability to OpenAPI versions prior to 3.2, allowing you to define a device authorization OAuth2 flow.
+
+It can appear as a property in the following objects: `{{page.objects|jsonify}}`.
+
+Used by: (informational)
+
+* [Microsoft.OpenApi](https://github.com/microsoft/OpenAPI.NET) (.NET OpenAPI library)
+{% endcapture %}
+
+{% capture example %}
+```yaml
+openapi: 3.1.0
+info:
+  title: My API
+  version: 1.0.0
+paths: {}
+components:
+  securitySchemes:
+    oauth2:
+      type: oauth2
+      flows:
+        x-oai-deviceAuthorization:
+          authorizationUrl: https://auth.example.com/authorize
+          tokenUrl: https://auth.example.com/token
+          x-oai-deviceAuthorizationUrl: https://auth.example.com/device
+          scopes:
+            read: Read access
+```
+{% endcapture %}
+
+{% include extension-entry.md summary=summary example=example %}