feat: form fields update

[nhsz]

Fixes https://github.com/ethereum/esp-website/issues/359

Previews

Fiat currency field

• /applicants/small-grants/apply
• /applicants/project-grants/apply

Countries of team multi-select

• /data-challenge-4844/apply

[nhsz]

@nhsz LGTM!

Only thing I noticed is this extra cross icon but not sure if this is related to this PR.

Fixed, thanks