uploadStickerFile method
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.
Implementation
Future<File> uploadStickerFile(String userId, HttpFile pngSticker) {
return _client.apiCall(_token, 'uploadStickerFile', {
'user_id': userId,
'png_sticker': pngSticker,
});
}