feat(pagination): style pagination component according to design specs

• Related issues:
  • #302 (closed)
  • #304 (closed)
  • #316 (closed)
  • #341 (closed)

What does this MR do?

Add missing styles to GitLab UI

Per #341 (closed), missing styles have been added to ensure that the pagination component looks the same with and without application.css.

Hide prev/next labels on mobile devices

As defined in #316 (closed), SCSS rules have been added to hide text labels for previous and next page items on mobile devices.

Update colors

Some of the colors used in the component didn't follow our specifications and have been replaced with the proper ones, as per #304 (closed).

Fix border bug on hover

The bug described in #302 (closed) has been addressed:

When a page is "active" in the pagination component, there is a gray boarder to the right of the active page. Curiously, this goes away when :hover is applied.

Screenshots

Desktop

Before	After

Mobile

Before	After