kate / katepart / KSyntaxHighlighting syntax highlighting for Twig
The Twig highlighting file was shamefully copied from the Django tpl syntax file.
Just copy the file to your katepart or KSyntaxHighlighting directory. Usually:
cp ./twig.xml ~/.kde4/share/apps/katepart/syntax/
or
/home/USER/.local/share/katepart5/syntax/
or (KDE Frameworks 5.29+)
~/.local/share/org.kde.syntax-highlighting/syntax/
The syntax directory may need to be created first.