feat(client): isGroup getter for Chat

packages/client/src/types/peers/chat.ts

@@ -156,6 +156,21 @@ export class Chat {
         return this._type!
     }
 
+    /**
+     * Whether this chat is a group chat
+     * (i.e. not a channel and not PM)
+     */
+    get isGroup(): boolean {
+        switch (this.type) {
+            case 'group':
+            case 'supergroup':
+            case 'gigagroup':
+                return true
+        }
+
+        return false
+    }
+
     /**
      * Whether this chat has been verified by Telegram.
      * Supergroups, channels and groups only