Support additional languages for highlight.js

highlight.min.js only includes 22 commonly used languages. E.g. Go and
Rust are not part of that set. This change allows users to add the JS
for additional languages via a config option.

I've also updated the library to the newest version.

exampleSite/config.toml

@@ -28,6 +28,7 @@ faviconfile = "img/leaf.ico"
 gatracker = "XYZ"
 github = "//github.com/you"
 highlightjs = true
+# highlightjslanguages = ["go"] # additional languages not included in the "common" set
 initials = "ad" # Displayed on single post page; DEPRECATED in v0.3.0.
 lang = "en"
 linkedin = "//linkedin.com/in/you"

layouts/partials/footer_scripts.html

@@ -13,7 +13,10 @@ try {
 {{ end }}
 
 {{ if .Site.Params.highlightjs }}
-  <script src="//cdnjs.cloudflare.com/ajax/libs/highlight.js/9.6.0/highlight.min.js"></script>
+  <script src="//cdnjs.cloudflare.com/ajax/libs/highlight.js/9.8.0/highlight.min.js"></script>
+  {{ range .Site.Params.highlightjslanguages }}
+    <script src="//cdnjs.cloudflare.com/ajax/libs/highlight.js/9.8.0/languages/{{.}}.min.js"></script>
+  {{ end }}
 
   <script type="text/javascript">
     hljs.initHighlightingOnLoad();

layouts/partials/head_includes.html

@@ -11,7 +11,7 @@
 <!-- CSS -->
 
 {{ if .Site.Params.highlightjs }}
-  <link rel="stylesheet" href="//cdnjs.cloudflare.com/ajax/libs/highlight.js/9.6.0/styles/default.min.css">
+  <link rel="stylesheet" href="//cdnjs.cloudflare.com/ajax/libs/highlight.js/9.8.0/styles/default.min.css">
 {{ end }}