added accessibility enhancements for details element
fixed js to detect if open close state
Set and update aria-hidden attribute
Add a secondary heading style for large headings
Use heading mixin for secondary heading style to increase spacing between secondary and main headings
Improve readability and adjust whitespace

Update check to see if detailsAttr is undefined
- Improve readability, as typeof undefined will always result in the
string 'undefined'

- Adjust whitespace
Remove bottom margin, as this is already set on the surrounding form-group
Update naming of date styles so they're not specific to date-of-birth
Pattern page to test form date

- Create test page with a single pattern
- Update routes.js
Move pattern test pages

- Move individual patterns to /patterns/ to show test pages
- Update routes.js
Change styling suggestion for validation

Having a red background can cause issues with the contrast ratio of validation text.