Original aria-describedby replaced with error message, instead of being added to it.

Problem/Motivation

When a validation occurs on an element, the aria-describedby is replaced with the error message. This removes the original aria-describedby, which in some cases is needed for context or other helpful information. The WCAG standard supports multiple aria-describedby by adding them in sequence with a space delimiter, so this module should also allow this.

Steps to reproduce

Enable the module.
Cause a form error validation with a field that has help text.

Proposed resolution

Append the error message to the end of the existing aria-describedby attribute using a space delimiter.