Updates from DIMES implementation

[HaSistrunk]

Changes to styles based on style library implementation in DIMES.

• Fix typos and clarify documentation
• Update checkbox styles to align boxes with labels and set checkbox size to match DIMES styles
• Update dropdown styles
• Adjust footer layout to right-align social icons
• box-sizing is set to border-box on the root html element in _base.scss, so adjust box-sizing at the component level only where needed.
• Adjust search form responsiveness
• Remove set line-height on the body element
• Adjust skip link styles to appear below the RAC header by default