[Bug] Nickname placeholder

[Nefariusek]

** Description **
Nickname placeholder does not disappear when input is clicked.

Steps to reproduce

1. Click 'Start Quiz'
2. Fill the form with settings and click 'START QUIZ'
3. Give random answers and confirm that you want to finish the quiz
4. Try to fill the 'NICKNAME' input
   5. Note that NICKNAME remains when input is focused. It does not disappear when the first characters are typed in.

Desired functionality
** NICKNAME should be just a placeholder of the input. It should be removed on focus. **

Screenshots

Additional informations
Use placeholder attribute.