Frontmatter to not auto-render LaTeX

[dreamalligator]

Add a Latex: off metadata, or a key to nullify the inclusion for the template. The default for the render_math plugin is to auto-insert and I think this is a good default, but maybe in the future someone will post something that it might interfere with.

An (easily solvable) example is on the join page where two dollar amounts flag the LaTeX mathjax script.

Can alternately write the hex html value of $ or dec $ because markdown renders all html, but I like options.

• pelican-plugins/render_math/#templates

While at it, make an option in the pelicanconf.py to either use the MathJax CDN or a locally hosted MathJax.js.

• render_math/math.py#L206