[Profiler] Add conditional profiling example config

[andreybolonin]

According to https://symfony.com/blog/new-in-symfony-5-4-profiler-improvements

[OskarStark]

Please rebase and fix the errors reported by DOCtor-RST, thanks

[andreybolonin]

@OskarStark done

[javiereguiluz]

Thanks Andrey!

While merging we did some changes because in this article we already have a section about enabling the profiler programmatically, so this section was similar and it's better to move it together. See 81a6e1a