runtime(tex): add texEmphStyle to texMatchGroup in syntax script

fixes: #16228

Co-authored-by: Github User JordL
Signed-off-by: Christian Brabandt <cb@256bit.org>

runtime/syntax/testdir/input/tex_01.tex

@@ -0,0 +1,14 @@
+\documentclass{article}
+\begin{document}
+\texttt{test}
+(\texttt{test})
+(  \texttt{test}   )
+\texttt{test})
+((blahblah)\\
+\texttt{test}
+\texttt{test}
+)
+(lorem ipsum)
+\texttt{test}
+( \textit{test} \textbf{test})
+\end{document}