create account form validation unicode

[intel-rrozestw]

My actions before raising this issue

• Read/searched the docs
• Searched past issues

https://cvat.org/auth/register
Type my first name or last name with unicode letters (ł and ń)

Expected Behaviour

First and last name fields were validated OK by some js validator.

Current Behaviour

First and last name fields display error with message "Please specify a first name".

Possible Solution

Adjust client side validators,

Steps to Reproduce (for bugs)

as described above.

Your Environment

https://cvat.org/auth/register now().

Next steps

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