adding back likert plugin
adding back likert plugin

andyh616/jsPsych,jspsych/jsPsych,wolfgangwalther/jsPsych,Scienthusiast/jsPsych,vergenzt/jsPsych,adrianoesch/jsPsych,andyh616/jsPsych,jodeleeuw/jsPsych,jspsych/jsPsych,shamrt/jsPsych,erikasf/jsPsych,wolfgangwalther/jsPsych,Scienthusiast/jsPsych,shamrt/jsPsych,jspsych/jsPsych,adrianoesch/jsPsych,vergenzt/jsPsych,erikasf/jsPsych,msrresearch/jsPsych,jspsych/jsPsych