Function bind

Declarative sends, by event delegation on root:

• data-scxml-send="name": send name. Default trigger: click; for a <form>, submit (default prevented; data = the form's fields); for <input>/<select>/<textarea>, change (data = { name, value }, plus checked for checkboxes and radios).
• A submit button with data-scxml-send inside a form names the event its submission sends (data = the form's fields): one form, several actions.
• data-scxml-on="dblclick keydown": override the trigger(s).
• data-scxml-data='{"json": true}': static data, merged over the dynamic data (invalid JSON: nothing is sent).
• data-scxml-session="<sessionId>" on the element or an ancestor: only that session reacts. Unmarked elements inside root go to every session bound to root.