add a code mirror to mytextarea field code example

Example: code mirros apply to all textareas

var textareas = document.querySelectorAll(".textarea-class");
for (var i = 0; i < textareas.length; i++) {
    CodeMirror.fromTextArea(textareas[i], {
        lineWrapping: true,
        mode: "javascript",
        theme: "neat",
        lineNumbers: true
     });
}