Improve navbar on smaller screen sizes

[calvinlu3]

Currently, the navbar items are left aligned, which introduces some extra spacing on the right when there is a line break. This causes the CDx nav item to appear shifted right.

One option is to make the nav items center aligned:

Another issue is that on a small screen, there is not enough margin to distinguish between adjacent nav items.

[calvinlu3]

Temporary solution:
We will text-align: center and remove Account for < 13'' laptops.

In the future, we want to explore "Mega Menu" to group certain pages together. (example: https://www.webstacks.com/blog/design-menu-navigation-ux-strategy)