Add a style guide to the Webform examples module

Problem/Motivation

Currently, the Webform example module provides kitchen sink examples for every possible element and feature, which is helpful for site builders and developers but is completely overwhelming to designers because it presents way too much information.

Proposed resolution

The Webform examples module should provide a style guide that includes baseline examples of all element variations. For example, there only needs to one example of a checkbox, radio button, and toggle element.

Remaining tasks

Style guide should include…

• All common elements and containers
• Enhance elements (ie select2, icheck, telephone, etc…)
• A basic composite element
• Inline messages
• Flexbox layout
• Wizard progress tracker.