Populate README

Author: jmduke

README.md

@@ -1 +1,8 @@
-# openapi
+This repository contains [OpenAPI specifications](https://www.openapis.org/) for [Buttondown](https://buttondown.email)'s API. You can find a more detailed API reference on Buttondown's [documentation site](https://docs.buttondown.email/api-reference/introduction).
+
+In addition to the core OpenAPI spec, this repository contains two supplementary files meant to improve the experience of writing against Buttondown's API:
+
+- `fixtures.json`, which contains test fixtures fore resources in the core spec.
+- `enums.json`, which contains detailed information about enums declared within the core spec. (This would ideally be subsumed into the spec itself, but [such a thing is not yet possible](https://github.com/OAI/OpenAPI-Specification/issues/348).)
+
+Changes to the API can be found in the [releases](https://github.com/buttondown-email/openapi/releases) section.

fixtures.json

@@ -6,6 +6,12 @@
     "url": "s3://buttondown/path-to-export",
     "status": "completed"
   },
+  "BulkActionOutput": {
+    "creation_date": "2019-08-24T14:15:22Z",
+    "id": "497f6eca-6276-4993-bfeb-53cbbbba6f08",
+    "url": "s3://buttondown/path-to-export",
+    "status": "completed"
+  },
   "ErrorMessage": {
     "code": "something_went_wrong",
     "detail": "Your call is very important to us."