Add the possibility to choose other events than just click

[brunosabot]

Hi,

This is a small contribution to be able to track via directives on other events than just the click.

Motivation

We got a form a bit complex, which has several fields.

We want to be able to determine the drop rate from inside the form to see if we are going in a wrong direction or if one specific form creates complexity for the user.

The rule to make it working is to track blur and/or focus events on the input fields.

Alternatives

We could have create a new method from inside our Vue component but we want to avoid any external behavior to be described from inside our component.

Directive are a much more efficient and clean way to achieve our tracking.

Choices made

To keep backwards compatibility and because it's the most obvious choice, we track by default on the click event.

[MatteoGabriele]

Hi @brunosabot
Thanks for your contribution. I will have a look and merge it asap!