adapt-youtube & adapt-vimeo iframes have no title attributes

[simondate]

Subject of the issue/enhancement/features

These components have no title attributes in their iframes. This should be here for screenreaders and is present in other 3rd party iframe components

wcag reference: https://www.w3.org/TR/WCAG20-TECHS/H64.html

Screenshots (if you can)

[oliverfoster]

Use aria-label instead, title is ambiguous as it doesn't behave the same way on iframes and other elements.

[simondate]

See adaptlearning/adapt_framework#2822