Make it possible to enable katex and mathjax globally in config.toml (#241)

* Add \\( and \\[ as mathjax delimiters

* Make it possible to enable katex and mathjax globally in config.toml

exampleSite/content/posts/render-latex-using-katex.md

@@ -14,6 +14,8 @@ katex = "true"
 +++
 ```
 
+If you want to enable KaTeX or MathJax for all post, add `katex = ture` or `math = true` in `config.toml` in `[params]` section.
+
 It's almost a dropin alternative to the mathjax solution,you should just choose one of them.  
 
 Inline math looks like this  

layouts/partials/posts/math.html

@@ -1,4 +1,4 @@
-{{- if .Params.math -}}
+{{- if or (.Params.math) (.Site.Params.math) -}}
   <script src="https://polyfill.io/v3/polyfill.min.js?features=es6"></script>
   <script type="text/javascript" async src="https://cdn.jsdelivr.net/npm/mathjax@3/es5/tex-mml-chtml.js"></script>
   <script src="https://cdn.jsdelivr.net/npm/mathjax@3/es5/startup.js" id="MathJax-script"></script>
@@ -17,7 +17,7 @@
     };
   </script>
 {{- end -}}
-{{- if .Params.katex -}}
+{{- if or (.Params.katex) (.Site.Params.katex) -}}
   <link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/katex@0.10.1/dist/katex.min.css" integrity="sha384-dbVIfZGuN1Yq7/1Ocstc1lUEm+AT+/rCkibIcC/OmWo5f0EA48Vf8CytHzGrSwbQ" crossorigin="anonymous">
   <script defer src="https://cdn.jsdelivr.net/npm/katex@0.10.1/dist/katex.min.js" integrity="sha384-2BKqo+exmr9su6dir+qCw08N2ZKRucY4PrGQPPWU1A7FtlCGjmEGFqXCv5nyM5Ij" crossorigin="anonymous"></script>
   <script defer src="https://cdn.jsdelivr.net/npm/katex@0.10.1/dist/contrib/auto-render.min.js" integrity="sha384-kWPLUVMOks5AQFrykwIup5lo0m3iMkkHrD0uJ4H5cjeGihAutqP0yW0J6dpFiVkI" crossorigin="anonymous"