Serve listings as array instead

PROTOCOL.md

@@ -107,28 +107,33 @@ Example response:
 
 ```json
 {
-    listings: {
+    listings: [
-      "tech": {
+      {
+          id: "tech",
           name: "Tech Communities",
           rooms: 5
       },
-      "privsec": {
+      {
+          id: "privsec",
           name: "Privacy & Security",
           rooms: 4
       },
-      "casual": {
+      {
+          id: "casual",
           name: "Casual Communities",
           rooms: 3
       },
-      "nsfw": {
+      {
+          id: "nsfw",
           name: "18+ Communities",
           rooms: 3
       }
-      "all": {
+      {
+          id: "all"
           name: "All Communities",
           rooms: 10
       }
-    }
+    ]
 }
 ```
 
@@ -140,4 +145,3 @@ Error responses:
 
 - `404 Not Found`
   - Returned if the given listing does not exist.
-