Update Component: Navigation - enable mega nav

[joesnellpdx]

Either enable a meganav option for the navigation component

Describe the solution you'd like @saltcod Please add acceptance / expectations

• links to examples
• options to consider
• depth of content
• how complex does it need to be?

Describe alternatives you've considered If needed, a new meganav component is a possible solution - but not ideal.

Please see https://github.com/10up/component-library/issues/45 and other navigation component issues before starting.