Currently we only support a very loose validation. There is now a
standard HTML5 element with matching regex. This will add the ability
to set a `mode` on the email validator. The mode will change the
validation that is applied to the field as a whole.
These modes are:
* loose: The pattern from previous Symfony versions (default)
* strict: Strictly matching the RFC
* html5: The regex used for the HTML5 Element
Deprecates the `strict=true` parameter in favour of `mode='strict'`
Billie Thompson
Amrouche Hamza
Christian Flothmann