show deprecated message for `friend` event

src/wechaty.ts

@@ -387,6 +387,18 @@ export class Wechaty extends Accessory implements Sayable {
                               : typeof listener,
                 )
 
+    // DEPRECATED for 'friend' event
+    if (event as any === 'friend') {
+      log.warn('Wechaty', 'on(friend) is DEPRECATED. use on(friendship) instead')
+      if (typeof listener === 'function') {
+        const oldListener = listener
+        listener = (...args: any[]) => {
+          log.warn('Wechaty', 'on(friend) is DEPRECATED. use on(friendship) instead')
+          oldListener.apply(this, args)
+        }
+      }
+    }
+
     if (typeof listener === 'function') {
       this.addListenerFunction(event, listener)
     } else {