Date input not supported on old browsers

[pettinarip]

Describe the bug

We are using <input type="date" /> in some places and that is not 100% supported by old browsers. It fallback to a input text, allowing the user to enter whatever they want.

To Reproduce
Steps to reproduce the behavior:

1. Use an old browser that doesn't support date inputs
2. Go to https://esp.ethereum.foundation/applicants/small-grants/apply
3. Select "Community Event" in "Project category"
4. The field "Event date" will fallback to an input text
5. Type whatever you want
6. Get error on submit

Expected behavior

We should have a workaround to normalize the input value when the input is not a date input.

Discuss
Should we support this issue? given that the partial support on browsers is 96.67%?

[nhsz]

IMO we shouldn't provide support for outdated browsers. Maybe we can add a 'please update your browser' message somewhere above the forms if we detect is old enough could help.