Add CAPTCHA for ticket submission

[apolignano]

This PR addresses https://embl.atlassian.net/browse/IBU-12438.

An HCaptcha React component now shows up on the feedback page. If validated, the submit button appears.

To address:

• I'm the one who created the HCaptcha account. It might be worth discussing how to have that account registered under a team/group email.

[apolignano]

hCaptcha group-level account created.

[matthiasblum]

Looks good overall, with one thing that needs to be changed.

At first, I ran the API and the client on my laptop, without being connected to the VPN (MySQL and Elastic connections going through SSH tunnels). Not being on the EBI network, the email failed to be sent to smtp.ebi.ac.uk: the following block raised an exception:

https://github.com/ProteinsWebTeam/interpro7-api/blob/2a78f22bea7353eb2db8e5d6ab6d7cd9db50944b/webfront/views/mail.py#L39-L46

Since it's not caught, the API returns a 500 and an "Invalid request" callout is displayed:

interpro7-client/src/subPages/Feedback/index.tsx

Lines 90 to 91 in e5a65ee

	setFeedbackText('Invalid request');
	setFeedbackType('warning');

Would it be possible to show an more informative error message, e.g.

Sorry, we couldn't send your feedback. You can submit it through our contact form instead. Please mention that you encountered a sending error.

[matthiasblum]

LGTM. Thanks!