the Add Media button should be a button

[afercia]

Currently, the Add Media button is a non-link link (with a href="#" attribute) and has a title attribute that repeats the link text:

For accessibility and semantics should be a button element. The current title attribute is redundant and doesn't add any useful information, should be removed. Worth noting when using ChromeVox it's impossible to open the media modal using the keyboard, whatever you try: pressing Enter or pressing Spacebar does nothing. While this has to do with some specific ChromeVox quirks with URL fragment links, events and preventing the default action, using a button instead of a link would fix it.

[afercia]

In the proposed patch:

• make the Add Media button a button and remove its redundant title attribute

[iseulde]

Looking good.

[iseulde]

In 33298:

Editor: Add Media should be a button

Props afercia.
Fixes #32969.