clase de hoy
- https://www.w3schools.com/tags/ref_eventattributes.asp
- https://www.w3schools.com/tags/tryit.asp?filename=tryhtml5_ev_onsubmit
- https://www.w3schools.com/tags/tryit.asp?filename=tryhtml5_ev_oninput
- https://www.w3schools.com/jsref/event_onsubmit.asp
- https://www.w3schools.com/jsref/tryit.asp?filename=tryjsref_onsubmit