Added link to OpenAPI documentation on GH pages

Signed-off-by: Christian Wolf <github@christianwolf.email>

docs/dev/api/index.md

@@ -0,0 +1,5 @@
+# OpenAPI documentation
+
+This page provides an overview over the possible API endpoints provided by the app. In the following are the various versions of the API linked:
+
+- [Version 0.0.2](0.0.2/index.html)

docs/dev/index.md

@@ -14,4 +14,9 @@ Instead we want to reference the official documentation on [docs.nextcloud.com](
 
 ## Frontend
 
-- [Webpack `BundleAnalyzer` Plugin](frontend/webpack-bundle-analyzer)
+- [Webpack `BundleAnalyzer` Plugin](frontend/webpack-bundle-analyzer)
+
+
+## Backend
+
+- [API endpoint documentation](api/index)