* Use named font sizes instead of values in px
* Convert rem mixin to em
* Remove unnecessary line-height
* 'Design' -> 'layout'
* Add comment to magic line-heihgt number
* Update a couple of class names to use BEM
* Use consistent name for SCSS variables
* Fix order summary line heights
* Update docs/contributors/coding-guidelines.md
Co-authored-by: Mike Jolley <mike.jolley@me.com>
Co-authored-by: Mike Jolley <mike.jolley@me.com>