8b16d8976f
- properly labels all the code editor areas (Theme/Plugin, Custom HTML widget, Additional CSS), whether CodeMirror is enabled or disabled - adds `role="textbox"` and `aria-multiline="true"` to the CodeMirror editing area to allow assistive technologies properly identify it as a textarea - standardizes the "keyboard trap" help text across the admin and keeps it as a list for better readability - use the Help text elements as target for `aria-describedby`, to make screen readers read out the help text when focusing the editors - fixes the `aria-expanded` attribute usage in the Customizer "Additional CSS" help toggle - moves focus to the CodeMirror editing area when clicking on the associated label - in the Plugin editor screen: changes a `<big>` element to `<h2>` for better semantics and consistency with the Theme editor screen - also, removes a few textdomain leftovers, see `better-code-editing` and `default` Props westonruter, melchoyce, afercia. Fixes #41872. git-svn-id: https://develop.svn.wordpress.org/trunk@41586 602fd350-edb4-49c9-b593-d223f7449a82