feat(mathjax): configure to let mathjax use local files

Close #63

exampleSite/config.toml

@@ -70,9 +70,12 @@ copyright = ""            # default: author.name ↓        # 默认为下面配
   toc = true                                                                            # 是否开启目录
   autoCollapseToc = false   # Auto expand and collapse toc                              # 目录自动展开/折叠
   fancybox = true           # see https://github.com/fancyapps/fancybox                 # 是否启用fancybox（图片可点击）
+
+  # mathjax
   mathjax = false           # see https://www.mathjax.org/                              # 是否使用mathjax（数学公式）
   mathjaxEnableSingleDollar = false                                                     # 是否使用 $...$ 即可進行inline latex渲染
   mathjaxEnableAutoNumber = false                                                       # 是否使用公式自动编号
+  mathjaxUseLocalFiles = false  # You should install mathjax in `yout-site/static/lib/mathjax`
 
   postMetaInFooter = true   # contain author, lastMod, markdown link, license           # 包含作者，上次修改时间，markdown链接，许可信息
   linkToMarkDown = false    # Only effective when hugo will output .md files.           # 链接到markdown原始文件（仅当允许hugo生成markdown文件时有效）

layouts/partials/scripts.html

@@ -78,7 +78,11 @@
       messageStyle: 'none'
     };
   </script>
-  <script type="text/javascript" async src="https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.2/MathJax.js?config=TeX-MML-AM_CHTML"></script>
+  {{ if .Site.Params.mathjaxUseLocalFiles -}}
+    <script type="text/javascript" async src="{{ "lib/mathjax/MathJax.js?config=TeX-MML-AM_CHTML" | relURL }}"></script>
+  {{- else -}}
+    <script type="text/javascript" async src="https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.2/MathJax.js?config=TeX-MML-AM_CHTML"></script>
+  {{- end }}
 {{- end }}
 
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