Added the VarDumper to the debug/debugging page

[hiddewie]

Issue #6342.

I've added a little example of the VarDumper component.

[snoek09]

Should we also add here how to use VarDumper in Twig?
Or should we instead link to components/var_dumper.rst?

[hiddewie]

I think the most important part about the VarDumper is its usage in PHP code. A link to the Components article is more useful in my opinion.

[wouterj]

Hi @hiddewie! Thanks for starting this!

I've taken your commit and included it in #7071. I've also did some minor rewrites of your text in that PR. Let me know what you think!

Thanks again, I hope to see more of these great PRs in the future!

[hiddewie]

Great, looks good!

Thank you!