Improve highlightjs usage to prevent report from lagging/crashing #527

[yong24s]

Fixes #527

hightlightjs (`hljs`) is used for highlighting of codes in code view
giving it context and readability. It can be triggered to render an
element with `window.hljs.highlightBlock(element)`.

`hljs` operations are expensive and stateless, where it re-renders even
on a rendered DOM and uses automatic detection of programming languages
if the language is not specified. Also, multiple `hljs` operations can
be triggered at once, causing the report to lag and crash.
Additionally, it seems to render regardless of trigger for any code in
`<pre><code>`. Furthermore, in our frontend, `vuejs` will trigger `hljs`
in `Vue#update`, when there is a data change, causing DOM to be 
re-rendered.

Let's optimize hljs usage, by triggering it when code is inserted into
the DOM, enclosing the code with a different tag, specifiying the
language to prevent expensive auto detection.

[yong24s]

@ongspxm

Can help me with the ESLint errors? 😢

I got it fixed. Just check if my fixes are correct. 😀

[yong24s]

@eugenepeh

For your preliminary testing, please.

[eugenepeh]

Excellent! 💯 👍

[yamidark]

Nice, much faster now 💯 👍 🥇

[ongspxm]

Excellante 👍

[ongspxm]

Minor nit, just set element.className to binding.value.split dun need make new var

[emer7]

I think HighlightJS doesn't highlight the syntax for subsequent contributor now:

Let's say there are 2 contributor A and B. Upon opening's A code panel it highlights the syntax but it doesn't highlight B's code panel.

Is it caused by this PR?

[eugenepeh]

@emer7 I am unable to replicate this. Would need you to provide more details. Note that adoc doesn't have much syntax highlighted as the other file types. If you suspect that this is caused by the PR, do use netlify to verify. To do so, visit the deploy url for this commit n the one before e.g. https://deploy-preview-533--reposense.netlify.com/, replace the 533 with target PR number.

[emer7]

Found it, turns out that problem itself is fixed by this PR. Sorry for the false alarm