[minimal-header-design/standalone_resource] nav bar /"pager" no worky on some configurations

[shawna-slh]

ATAG Report Tool was approved to use a horizontal scroll bar for the nav bar when it doesn't fit in the viewport with the text size. Subsequent designs used that as well: ACT Rules, Supplemental Guidance, WCAG-EM Report Tool redesign, and WCAG upcoming.

Unfortunately:

• the horizontal scrollbar doesn't appear by default in Chrome macOS (it does sometimes based on users settings)
• the horizontal scrollbar is barely visible in Safari iOS

(EOWG participants can provide examples as useful)