highlightjs : include only on pages with mainSections

* this makes hljs not load on index, taxonomies, archive
pages where code highlighting isn't used
* improving page site load time

layouts/partials/footer.html

@@ -12,9 +12,10 @@
             <path d="M12 6H0l6-6z" /></svg>
     </button>
 </a>
-
+{{if in site.Params.mainSections .Type }}
 {{ $highlight := resources.Get "js/highlight.min.js" | minify | fingerprint}}
 <script src="{{ $highlight.Permalink }}" integrity="{{ $highlight.Data.Integrity }}"></script>
+{{end }}
 <script>
     window.onload = function () {
         if (localStorage.getItem("menu-scroll-position")) {