language for hyphenation with tufte_handout template

rmarkdown

#1

I am trying to include a package in a tufte_handout file, and I do not manage.
Here is my example, please tell me whats wrong with it.

-=-=-=-=-=-=-=-=-=

--
title: "Including packages in Tufte handout"
output:
  tufte::tufte_handout:
    latex_engine: xelatex
    extra_dependencies: ["babel"]
    keep_tex: true
---


A very simple test for using packages. In LaTeX I would use `\usepackage[german]{babel}`. How can I do this in the YAML preface?

# Hyphenation

Es ist ja Teil der Allgemeinbildung, zu wissen, dass in einer Gruppe von 23
Leuten die Wahrscheinlichkeit, dass mindestens 2 ihren Geburtstag am selben Tag haben,
größer als $\frac{1}{2}$ ist.

#2

I managed to get the hyphenation I need in "oldfashioned" style, using

output:
  tufte::tufte_handout:
    latex_engine: xelatex
    includes:
      in_header: mystyle.sty

and mystyle.sty contining

\usepackage[ngerman]{babel}