Make configurable

For example I would like to use this https://github.com/hakimel/reveal.js/#configuration

to make center: false

Is there a place where I can set the configuration?

additionally perhaps a way to change the CSS? In case I want the font sizes to be different for example.

Not at the moment, that's a good opportunity for improvement