Updated code to allow sidenav expand on click

[alexjanousekGSA]

Navbar improvements

• When clicking on About Notify, a subnav will now open that maintains style consistency with its parent links.
• Header navbar is updated with active state when sublinks are clicked.
• This overrides uswds default components

[alexjanousekGSA]

The changes made here to allow a larger width for the sidenav affected all sidenavs globally and pushed content to the side. BackstopJS highlighted this well and we are discussing now if we will keep the width or make it a case by case basis. In this specific screenshot you can see some content needs a slight update to fit in the smaller space.