feat(api): expose Discord statistics on /private/meta

PluralKit.API/APIJsonExt.cs

@@ -9,7 +9,7 @@ namespace PluralKit.API;
 
 public static class APIJsonExt
 {
-    public static JObject ToJson(this ModelRepository.Counts counts)
+    public static JObject ToJson(this ModelRepository.Counts counts, int guildCount, int channelCount)
     {
         var o = new JObject();
 
@@ -19,6 +19,10 @@ public static class APIJsonExt
         o.Add("switch_count", counts.SwitchCount);
         o.Add("message_count", counts.MessageCount);
 
+        // Discord statistics
+        o.Add("guild_count", guildCount);
+        o.Add("channel_count", channelCount);
+
         return o;
     }
 }