[gnosis.io] Add cookie banner

[giacomolicari]

In line with global cookie policies we should add a cookie banner on the website.

Example: https://webflow.com/made-in-webflow/website/free-clone-gdpr-cookie-consent-banner

[giacomolicari]

Free Webflow component for the cookie banner: https://finsweet.com/cookie-consent

[giacomolicari]

Cookie banner and the policy have been implemented:

• Banner now visible at https://www.gnosis.io/
• Policy available at https://www.gnosis.io/cookie-policy