[TASK] Add HTML5 checks for "create new admin user" in Install Tool

This patch adds HTML5 attributes to the form fields so the username
field is set to required and the password has to be at least 8
characters long.

Resolves: #82135
Releases: master
Change-Id: I3ab05af63125479de2427a5b236f8c434d598aad
Reviewed-on: https://review.typo3.org/54872


Reviewed-by: Benni Mack <benni@typo3.org>
Tested-by: Benni Mack <benni@typo3.org>
Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Susanne Moog <susanne.moog@typo3.org>
Tested-by: Susanne Moog <susanne.moog@typo3.org>