runtime(zserio): add zserio syntax (#13005)

Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/runtime/synmenu.vim b/runtime/synmenu.vim
index 9a6ec99..5251045 100644
--- a/runtime/synmenu.vim
+++ b/runtime/synmenu.vim
@@ -645,6 +645,7 @@
 an 50.170.410 &Syntax.WXYZ.YAML :cal SetSyn("yaml")<CR>
 an 50.170.420 &Syntax.WXYZ.Yacc :cal SetSyn("yacc")<CR>
 an 50.170.440 &Syntax.WXYZ.Zimbu :cal SetSyn("zimbu")<CR>
+an 50.170.440 &Syntax.WXYZ.Zserio:cal SetSyn("zserio")<CR>
 
 " The End Of The Syntax Menu