Add an API endpoint for image/png

[iamansuman]

I'm making a Telegram bot where a user queries for a GitHub user and the bot returns the stat.
I found this repo just right for my project but when I checked the HTTP response, the mime type was image/svg+xml; charset=utf-8

telebot.TeleBot().send_photo() does not supports svg

It will be good to add an endpoint for image/png mime type.
Although it will be static with no animations, it can be universally accessed.

[rickstaa]

@iamansuthecoda a feature request for this can be found in #624.