missing is_ephemeral on BotCommand

[ivanfmartinez]

The BotCommand class miss the is_ephemeral attribute

https://core.telegram.org/bots/api#botcommand

• is_ephemeral Boolean Optional. True, if the command sends an ephemeral message, which can be seen only by the sender of the message and the bot

[mircoianese]

Added by Telegram in version 10.2.

Last version of this library is 10.1. Soon to be updated to latest version 10.3 (#440)