[feature] Add aria-label to wcm-modal component

[cashd]

What problem does this new feature solve?

The wcm-modal component does not pass accessibility standards for dialogs because it is missing an aria-label. I ran an accessibility test using Google Lighthouse and it raised this issue.

Here is a reference to the accessibility standard https://dequeuniversity.com/rules/axe/4.9/aria-dialog-name

Describe the solution you'd like

Add an aria-label property to the wcm-modal component to satisfy accessibility requirements for users with screen readers.