Example with uploading sound data

[jirilukavsky]

This is just a small thing - the code uses subject_id defined in the first example, but it is omitted in the second example.

Because some basic things like loading the plugin are mentioned, people may expect the code is a complete working example. In other words, the example should include:

const subject_id = jsPsych.randomization.randomID(10);

[jodeleeuw]

thanks this is a great point!