Link & Pill shaped nav items height

[pricop]

Currently, the nav-link and nav-pills items sit at 36px in height. This is due to having no border around them.

By contrast, nav-tabs, and nav-underline, have a height of 38px (2.25rem), this is because nav-tabs have a 1px border around them, while nav-underline have 2px underneath each element.

My proposed change is to increase the height of nav-link and nav-pills to 38px, by adding an invisible border to match the height of nav-tabs and nav-underline counterparts.

Additionally, it's super common to use an in-page nav alongside a search input component, or an additional button component (that's outside the scope of the nav itself), for example:

Before

After

This will make all nav variants (link, pill, tab, underline) cohesive, having the same height across the board, regardless of each version is used.

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I've done a PR with the change for you guys to have a look at: #42146