Add support for common useful tokens

We want Patternkit to be useful out of the box for moderately complex Drupal site builds.

This includes things like paragraphs and responsive images, so our options are:

• Add an issue to the respective projects to get the needed tokens added
• Add an issue to the Token module for the needed token support
• Add the needed token support to Patternkit

We want to evaluate a combination of these options for the following common scenarios:

• Multiple-nested paragraphs
• Responsive images attributes
• Link attributes
• File fields
• Any core field types missing a :raw token modifier

Some of these scenarios may already have tokens and in that case all we need to do is document them in the readme.