plain and simple, this is how i added the opendyslexic font toggle.
this isn't really a tutorial, just how to add your own.
firstly, i put this code right after my body tag. it adds the button and its functionality.
please look in the source code for this part, i can't get inline code to work.
secondly, please give your body tag the id of "bodyy". (body id="bodyy")
lastly, to your CSS or wherever, add the font family: