Make contact_method entity themeable

Problem/Motivation

Currently the "contact method" entities do not have their own dedicated theme templates.
I would like these to exist, since I want to adapt the theming of my contact methods.

For example, I want to override the template for the Telephone contact type, to be rendered as follows:

<div>{{ telephone }} ({{ detail }})</div>

This would then output a telephone contact method as:

+32 1234 56 78 90 (Home)

Proposed resolution

• Add a theme hook
• Add a template file
• Add theme suggestions for bundle & view mode combinations