[documentation] Manage inconsistency in themes

[Kieran Lal]

Hello, the number one most difficult issue according to the Drupal  
administration user experience survey is "Manage inconsistency in  
themes".

I am proposing we add a section to the customization and  
configuration handbook to address this.

We should talk about how to debug your theme and what tools will help  
you.

There is one spot left in the configuration and customization home  
page.  Any objections if I use that?

Kieran