Add the ability to enable/disable Latex "display mode".

[gbmhunter]

As mentioned in the KaTeX readme:

Rendering options

You can provide an object of options as the last argument to katex.render and katex.renderToString. Available options are:

displayMode: boolean. If true the math will be rendered in display mode, which will put the math in display style (so \int and \sum are large, for example), and will center the math on the page on its own line. If false the math will be rendered in inline mode. (default: false)

It would be great to enable/disable this with something like:

<Latex displayMode={true}>$y = x$</Latex>