Highlight math not using TeX but TeX math

Fix #236

autoload/vimwiki/base.vim

@@ -1079,6 +1079,14 @@ function! vimwiki#base#nested_syntax(filetype, start, end, textSnipHl) abort "{{
   else
     unlet b:current_syntax
   endif
+
+  " Fix issue #236: tell Vimwiki to think in maths when encountering maths
+  " blocks like {{$ }}$. Here, we don't want the tex highlight group, but the
+  " group for tex math.
+  if a:textSnipHl ==# 'VimwikiMath'
+    let group='texMathZoneGroup'
+  endif
+
   execute 'syntax region textSnip'.ft.
         \ ' matchgroup='.a:textSnipHl.
         \ ' start="'.a:start.'" end="'.a:end.'"'.