metadata rendering: add mathjax javascript to data package rendering

[mobb]

Some datasets will have equations in mathML or LaTeX in text fields. MathJax has functions to display these. Here is the script include from the old stylesheets:

<script src="https://cdn.mathjax.org/mathjax/latest/MathJax.js?config=Te
X-MML-AM_CHTML"></script>

We should add this to the rendering of our data packages. Here is a data package with equations in the metadata (methods section), for testing: packageid=knb-lter-sbc.103.3