Use this method to upload a .PNG file with a sticker for later use in createNewStickerSet and addStickerToSet methods (can be used multiple times). Returns the uploaded File on success.
This object represents a file ready to be downloaded. The file can be downloaded via the link https://api.telegram.org/file/bot<token>/<file_path>. It is guaranteed that the link will be valid for at least 1 hour. When the link expires, a new one can be requested by calling getFile.
Maximum file size to download is 20 MB