Provide an option to include third party libraries in the build and specify them in the document header

[dominicfollett]

I'm trying to use a well-established third party library for managing gifs in my presidium site. I have no option to include the library in the build ... this means that I need to make a request for it, but this is NOT allowed in the secure environment this documentation is published in.

Moreover, the only way for me to include the library is to paste this

<script src="https://unpkg.com/freezeframe/dist/freezeframe.min.js"></script>

in every markdown article, I need it in. I would like to be able to include this script tag only once. Preferably, I should have an option where I can append it to the document header.