Add description to OpenAPI import example (#224)

Author: svix-lucho

docs/event-types.mdx

@@ -211,6 +211,7 @@ In addition to the standard features supported by the OpenAPI spec, Svix also su
   "pet.new": {
     "post": {
       "operationId": "pet.new",
+      "description": "A new pet has been created",
       "x-svix-feature-flag": "beta-feature-a",
       "x-svix-group-name": "group-name-1",
       "requestBody": {