a11y: Create Accessibility test suite using Cypress

[scures]

Is your feature request related to a problem? Please describe.

We're looking at working on accessibility issues, such as #7968

Describe the solution you'd like

It's important that once the changes are made, we implement some a11y tests to make sure no new issues are introduced.
Since we already use Cypress for E2E testing, we could make use of the AXE plugin which allows to test for some WCAG standards such as color-contrast, heading-order, image-alt & `label.
The first step would by to get the configuration ready to write those tests.

There is an Axe plugin for Cypress and also one from IBM (https://www.npmjs.com/package/cypress-accessibility-checker)

Also see: https://www.deque.com/blog/how-to-test-for-accessibility-with-cypress/

Additional context

AXE: The Standard in Accessibility Testing
WCAG: Web Content Accessibility Guidelines (WCAG) 2.1 covers a wide range of recommendations for making Web content more accessible.

[aalves08]

This PR #12900 fits the issue