doc: fix latexpdf build

Building pdf was broken because of chinese characters in one of the
code snippets.

LaTeX stack exchange recommends use XeTeX engine instead but this
causes other formatting problems (like footer using wide font) so
just hacking this in for now.

doc/api/hubs_ev3brick.inc

@@ -163,8 +163,16 @@
 
             **Example: Say hello... in several ways.**
 
+            .. raw:: latex
+
+               \begin{CJK}{UTF8}{gbsn}
+
             .. literalinclude:: ../../pybricks-projects/snippets/ev3/screen_print/main.py
 
+            .. raw:: latex
+
+               \end{CJK}
+
     .. automethod:: pybricks.hubs::EV3Brick.screen.set_font
 
         **Example:** See example in :meth:`print`.

doc/common/conf.py

@@ -199,6 +199,7 @@ latex_elements = {
     # Additional stuff for the LaTeX preamble.
     #
     'preamble': r'''
+    \usepackage{CJKutf8}
     \makeatletter
     \fancypagestyle{normal}{
         \fancyhf{}