readme.md: update schema

readme.md

@@ -5,25 +5,30 @@ This repo contains backing information for Glowers Radio.
 The `songs.json` format **is only intended for use for Glowers Radio**, and is effectively a living standard as a result. **Live data may change drastically without warning**
 
 ```yaml
-required: [ id, sources ]
+required: [ version, songs]
 properties:
-  id:
+  version: { type: integer }
-    type: string
+  songs:
-  tags:
-    type: array
-    items: [ { type: string } ]
-  metadata:
-    required: [ title, artist ]
-    properties:
-      title: { type: string }
-      artist: { type: string }
-  sources:
-    type: array
     items:
-    - required: [ type, url ]
+      required: [ id, sources ]
       properties:
-        type: { type: string, format: mimetype }
+        id:
-        url: { type: string, format: uri }
+          type: string
-        thumbnail_type: { type: string }
+        tags:
-        thumbnail_url: { format: uri }
+          type: array
+          items: [ { type: string } ]
+        metadata:
+          required: [ title, artist ]
+          properties:
+            title: { type: string }
+            artist: { type: string }
+        sources:
+          type: array
+          items:
+          - required: [ type, url ]
+            properties:
+              type: { type: string, format: mimetype }
+              url: { type: string, format: uri }
+              thumbnail_type: { type: number }
+              thumbnail_url: { format: uri }
 ```