Navbar: add $navbar-nav-link-padding-y

Created by: royklutman

Is it an idea to add $navbar-nav-link-padding-y to the navbar links?

_navbar.scss currently only sets the x-padding: https://github.com/twbs/bootstrap/blob/a194abbb5aaa999f5c0eba4bba4f7aff6ab2d0ad/scss/_navbar.scss#L165-L168 The y-padding is currently inherited from _nav.scss: https://github.com/twbs/bootstrap/blob/a194abbb5aaa999f5c0eba4bba4f7aff6ab2d0ad/scss/_nav.scss#L14-L26

Thanks!