core/tg: High level Telegram API

surdeus e62ccf5780 feat: better document sending handling with more general io.Reader interface to get the data.		10 月之前
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cat.jpg	522b9ada02 A bit more of refactoring and added way to send image files.	1 年之前
gopher.png	6c491fc04a Fixed the image.	1 年之前
hello.txt	e62ccf5780 feat: better document sending handling with more general io.Reader interface to get the data.	10 月之前