fix: make asSystemMessage spit out ownership change

package.json

@@ -1,6 +1,6 @@
 {
     "name": "revolt.js",
-    "version": "6.0.8",
+    "version": "6.0.9",
     "main": "dist/index.js",
     "typings": "dist/index.d.ts",
     "module": "esm/index.js",

src/maps/Messages.ts

@@ -112,6 +112,8 @@ export class Message {
                 return { type, by: get(system.by) };
             case "channel_icon_changed":
                 return { type, by: get(system.by) };
+            case "channel_ownership_changed":
+                return { type, from: get(system.from), to: get(system.to) };
         }
     }