reveal.js template: include tex2jax configuration.

This ensures that we don't use $..$ delimiters, which
gives bad results when $ is used as a currency sign.
This depends on the current dev version of reveal.js.

data/templates/default.revealjs

@@ -234,6 +234,18 @@ $if(mathjax)$
         math: {
           mathjax: 'https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.0/MathJax.js',
           config: 'TeX-AMS_HTML-full',
+          tex2jax: {
+            inlineMath: [['\\(','\\)']],
+            displayMath: [['\[','\]']],
+            balanceBraces: true,
+            processEscapes: false,
+            processRefs: true,
+            processEnvironments: true,
+            preview: 'TeX',
+            skipTags: ['script','noscript','style','textarea','pre','code'],
+            ignoreClass: 'tex2jax_ignore',
+            processClass: 'tex2jax_process'
+          },
         },
 $endif$