Design Pattern Library - Component: Links

Add a new component for links.

This should include documentation related to styles and usage of anchors as well as documentation regarding truncation of links.

Transfer/update existing information regarding anchors: https://docs.gitlab.com/ee/development/ux_guide/components.html#anchor-links

Related: gitlab-org/gitlab-design#122 (closed)

• Buttons vs links: https://gitlab.com/gitlab-org/gitlab-ce/issues/21287#note_17099288
• https://gitlab.com/gitlab-org/gitlab-ce/issues/21287#note_16963426