Email fields should only accept valid email addresses

[mfb]

Email fields should only accept valid email addresses. This validation could happen in the browser, and should also be enforced by server-side code. Currently it appears there is no client or server-side validation, when using the congress email tool form. The petition form does appear to have email validation. I didn't yet test other forms.

[mfb]

Note: The email field correctly uses "email" input type, but because it's not a normal form submit, validation will need to manually be added to the form.