Enhance a11y on focus and buttons

[dascritch]

• [x] Check play/pause button keyboard behaviour
• [x] Add :focus special outline, var()
• [x] Switch button's aria-title on visible svg title
• [x] ARIA progressbar elements do not have accessible names

[dascritch]

We must style the whole WebComponent focus outline. And hide the shadow one.

[dascritch]

We don't really need it, as we already have focus, hover rules https://ricardozea.medium.com/how-to-remove-the-blue-border-outline-in-chrome-safari-and-dotted-line-in-firefox-edge-fe5e2155d44c

If there is a need of focus color, we should have it on the whole component, and so we don't need a css variable

I would try to remove the blue halo of Safari, to document how to make it.