cc-header-orga: hide initials from screen readers

[florian-sanders-cc]

Context

When the organization has no avatar, the cc-header-orga component displays the organization initials instead.

It relies on the accessible-name (previously named text) to do so but this means screen reader users may hear graphic CC for the Clever Cloud logo for instance.

This is not a big deal but both initials or the image could be considered decorative and we could avoid creating confusion by simply hiding these from screen readers.

Solution

• When the org has an avatar, keep on relying on the cc-img but without setting an accessible-name.
• When the org has no avatar, rely on a custom <span aria-hidden="true"> from within the cc-header-orga component to insert the initials.