fix(readme): add an import of TEXT (#318)

Author: jtr109

README.md

@@ -207,7 +207,7 @@ import itchat
 newInstance = itchat.new_instance()
 newInstance.auto_login(hotReload=True, statusStorageDir='newInstance.pkl')
 
-@newInstance.msg_register(TEXT)
+@newInstance.msg_register(itchat.content.TEXT)
 def reply(msg):
     return msg.text
 

README.rst

@@ -206,7 +206,7 @@ You may use the following commands to open multi instance.
     newInstance = itchat.new_instance()
     newInstance.auto_login(hotReload=True, statusStorageDir='newInstance.pkl')
 
-    @newInstance.msg_register(TEXT)
+    @newInstance.msg_register(itchat.content.TEXT)
     def reply(msg):
         return msg['Text']
 

README_EN.md

@@ -207,7 +207,7 @@ import itchat
 newInstance = itchat.new_instance()
 newInstance.auto_login(hotReload=True, statusStorageDir='newInstance.pkl')
 
-@newInstance.msg_register(TEXT)
+@newInstance.msg_register(itchat.content.TEXT)
 def reply(msg):
     return msg['Text']