The required marker in forms (*) should have a screen reader text to explain the field is required

Problem/Motivation

We show a red asterisk (*) on fields that are required. However, for screenreaders we do not have any text.

Steps to reproduce

Compare the Open Social login form to the Drupal.org login form

Proposed resolution

Add a title to the asterisk element, similar to the Drupal.org login form.

Remaining tasks

User interface changes

API changes

Data model changes