Update summary on project page for compatibility with Project Browser

Problem/Motivation

A short, non-technical description has been created by the community for your module for compatibility with Project Browser. The short description will be displayed on the cards in the Project Browser grid and list views.
Requirements: The short description (200 characters or less) should answer the question - "what does this module do in a non-technical way". Do not use the module name in the short description.

Proposed resolution

Allows different backends for formatting and sending e-mails by default, per module, and per mail key. Additionally, enables configuration of a theme to be used for sending e-mails.

Remaining tasks

MAINTAINERS: Please consider adding the proposed short description as the Summary for the Description field on your project page. Please click “Edit summary” near your description field to add the short description.