Add human verification to avoid spam contact forms.

[jorgeteixe]

We are receiving many emails like the following:

We should implement a solution to avoid spam form deliveries.

[jorgeteixe]

I send a reminder because we are receiving quite a bit of spam.

@gpul-org/web-maintainers

[GamuWasTaken]

We have been looking into it, currently we are a bit busy with exams, for the moment I've changed the handler to filter out spamy looking messages (the get saved, just not sent)