Move inline JavaScript into files

The inline JS is all pretty much loaded on $(document).ready ($(function() is a short-hand) so I see no reason why you can't move it out of the head and into files. Now why do this? It's good practice to add a Content-Security-Policy tag to mitigate XSS attacks and inline JS is an attack vector. Once the inline JS is gone, consider adding something like this:

<meta http-equiv="Content-Security-Policy" content="upgrade-insecure-requests;
 default-src 'self';
 script-src 'self' https://cdnjs.cloudflare.com;
 style-src 'self' fonts.googleapis.com;
 font-src 'self' fonts.googleapis.com;">

Might need refining depending on what gets blocked.

I'll avoid opening a PR for now, but you can see the commits I've made here: https://github.com/remyabel/CppCoreGuidelines/tree/gh-pages

There are some problems so far:

• The anchor library injects inline CSS, which means we have to allow unsafe-inline, not ideal

• Similarly there's a font being loaded in as a data: somewhere. Allowing data: is unsafe since it allows arbitrary data to be injected

Both of these effectively render CSP useless, thus I doubt this will be made into a PR. Although I'm happy to suggest workarounds if interested.