[#1116] Code Panel: weird syntax highlighting (#1521)

RepoSense frontend is using `highlightjs@9.14` which has some 
highlighting issues.

These issues were fixed by the following PR in `highlightjs`:
highlightjs/highlight.js#2531

Let's update `highlightjs` to `10.7.1` in RepoSense.

Author: gerhean

frontend/src/index.pug

@@ -6,7 +6,7 @@ html
     link(rel="stylesheet", href="https://fonts.googleapis.com/css?family=Titillium+Web")
     link(rel="stylesheet", href="https://cdn.jsdelivr.net/npm/normalize.css@8.0/normalize.min.css")
     link(rel="stylesheet", href="https://cdn.jsdelivr.net/npm/muicss@0.9/dist/css/mui.min.css")
-    link(rel="stylesheet", href="https://cdn.jsdelivr.net/npm/highlight.js@9.14/styles/color-brewer.min.css")
+    link(rel="stylesheet", href="https://cdn.jsdelivr.net/npm/highlight.js@10.7.1/styles/color-brewer.min.css")
     link(rel="stylesheet", href="https://cdn.jsdelivr.net/npm/vue-loading-overlay@3/dist/vue-loading.css")
     link(rel="stylesheet", href="static/css/panels.css")
     link(rel="stylesheet", href="static/css/style.css")
@@ -26,12 +26,12 @@ html
     script(src="https://cdn.jsdelivr.net/npm/vue@2.5/dist/vue.js")
     script(src="https://unpkg.com/vuex@3.1.3/dist/vuex.js")
 
-    script(src="https://cdn.jsdelivr.net/gh/highlightjs/cdn-release@9.14/build/highlight.min.js")
-    script(src="https://cdn.jsdelivr.net/gh/highlightjs/cdn-release@9.14/build/languages/asciidoc.min.js")
-    script(src="https://cdn.jsdelivr.net/gh/highlightjs/cdn-release@9.14/build/languages/gradle.min.js")
-    script(src="https://cdn.jsdelivr.net/gh/highlightjs/cdn-release@9.14/build/languages/plaintext.min.js")
-    script(src="https://cdn.jsdelivr.net/gh/highlightjs/cdn-release@9.14/build/languages/scss.min.js")
-    script(src="https://cdn.jsdelivr.net/gh/highlightjs/cdn-release@9.14/build/languages/yaml.min.js")
+    script(src="https://cdn.jsdelivr.net/gh/highlightjs/cdn-release@10.7.1/build/highlight.min.js")
+    script(src="https://cdn.jsdelivr.net/gh/highlightjs/cdn-release@10.7.1/build/languages/asciidoc.min.js")
+    script(src="https://cdn.jsdelivr.net/gh/highlightjs/cdn-release@10.7.1/build/languages/gradle.min.js")
+    script(src="https://cdn.jsdelivr.net/gh/highlightjs/cdn-release@10.7.1/build/languages/plaintext.min.js")
+    script(src="https://cdn.jsdelivr.net/gh/highlightjs/cdn-release@10.7.1/build/languages/scss.min.js")
+    script(src="https://cdn.jsdelivr.net/gh/highlightjs/cdn-release@10.7.1/build/languages/yaml.min.js")
   body
     #app
       loading-overlay.overlay-loader(