feat: Add get account quota, and get number of sent messages.

[stu01509]

Add feature to get number of sent messages.

• getQuota - Gets the target limit for additional messages in the current month.
• getSentReplyMessage - Get number of sent reply messages
• getSentPushMessage - Get number of sent push messages
• getSentBroadcastMessage - Get number of sent broadcast messages
• getSentMulticastMessage - Get number of sent multicast messages

[WayneChang65]

@stu01509 Hi Cliff, Thanks for your PR for our linebot users. The functions you added, the name like get"Send"ReplyMessage change to be getSentReplyMessages could make sense a bit. (getNumOfSentReplyMessages or getSentReplyMessagesCount could be better but a bit long~) Because that means it's used for getting number of has already sent messages. On the other hand, if it's possible, please add example codes to demo.js. That'll help users use them easily. Finally, do not forget code for test. Any ideas?

[boybundit]

Thanks! 😄