Update button styling
Update button styling

msrresearch/jsPsych,jspsych/jsPsych,shamrt/jsPsych,jspsych/jsPsych,shamrt/jsPsych,wolfgangwalther/jsPsych,jspsych/jsPsych,jspsych/jsPsych,wolfgangwalther/jsPsych,jodeleeuw/jsPsych