How can I define the engine XeLaTex through Overleaf API?

According to the official documentation, 'By default, Overleaf tries to detect which TeX engine to use, and it usually chooses pdflatex. If you would like to set the engine explicitly for your new project, you can pass an engine parameter with one of the following values: latex_dvipdf, pdflatex, xelatex or lualatex.'. My project has to be compiled with xelatex. So, considering the given the MWE:

<form action="https://www.overleaf.com/docs" method="post" target="_blank">
<input type="text" name="snip_uri"
       value=开发者_StackOverflow社区"https://production-overleaf-static.s3.amazonaws.com/examples/helloworld.tex"><br>
<input type="submit" value="Open in Overleaf">
</form>

where/how do I set the engine parameter to xelatex through the API (and not by the overleaf menu settings)?

I have tried changing the first line of main.tex to %!TeX program = xelatex, but had no success.