[FieldTypes] add vars option on DateTime & Twig field types

[loic425]

Passing generic "vars" option on string & datetime fields could be useful.

->addField(
      StringField::create('contractNumber')
          ->setOption('vars', ['th_class' => 'text-end'])
  )

When using this grid on twig rendering, you can handle these vars.
But you can also define some vars on other rendering like a CLI rendering option that could be useful too.