Make sure the debug:* commands are documented

[weaverryan]

This is especially important after #8538, where I killed the debugging article. See #7071 for a list of most or all of the commands.

I want to put these inside their relevant sections.

• debug:config (this should be put at the top of every reference article)
• debug:container
• debug:form
• debug:event-dispatcher
• debug:router
• debug:translation
• debug:twig
• about