[Security] Better explain the Remember Me functionality

[whitezo]

Hi,
Working my way through the Symfony 5.2 security documentation and installation process I've found an issue that took me a couple of hours to figure out.

https://symfony.com/doc/current/security/remember_me.html

The remember me functionality described above should mention that for this to work the LoginFormAuthenticator (created via make) should add a RememberMeBadge to the Passport in the authenticate function.

I've only figured this out after looking at the logs, finding the message saying that remember me was skipped and then searching the source for that message, and what was causing it.

[javiereguiluz]

Closing in favor of #15908, a meta-issue that groups all pending security-related issues so we can easily check them.