Due to the variety of link / button styles a theme can possess, variants of links / buttons are differentiated using letters.
For button styles, variants begin at A (A representing the primary button type) and working upwards.
For link styles, variants are prefixed with an underscore, e.g. _A, _B etc.
As email and phone link user interaction is often something clients wish to track with analytics, classes for phone and email links should include
link-tel and link-email respectively. This allows for easy targeting of all phone / email links when adding analytics events that can be used
to track user interaction. link-tel and link-email can be added using the ANALYTICS_LINK_EVENT_CLASSES object found in #utils/constants.ts.