[DOCS] Add example to use 403 ErrorRedirectHandler for login redirects

This patch shows an example for the frontend login
how to get a redirect when an unauthorized visitor
tries to access a restricted page.

In this case, a 403 ErrorHandler can perform a
redirect with special parameters, that a properly
configured felogin plugin can utilize to
redirect back to.

Resolves: #104694
Related: #101252
Releases: main, 12.4, 11.5
Change-Id: Ia2c6723621304b8b3de366590c1be905572b00d1
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/85817


Reviewed-by: Garvin Hicking <gh@faktor-e.de>
Reviewed-by: Georg Ringer <georg.ringer@gmail.com>
Tested-by: Garvin Hicking <gh@faktor-e.de>
Tested-by: Georg Ringer <georg.ringer@gmail.com>