Update: Align 'skip to transcript' styles with Media (fixes #36)

[swashbuck]

Fixes #36

Update

Align the "skip to transcript" button styles with the latest Media component accessibility approach:

• Replace the :not(:focus-visible) visually-hidden rules with the core .visually-hidden-focusable mixin.
• Add margin-bottom: @item-margin so the button has spacing when focused and visible.

Testing

1. Build a course with a YouTube component that has a transcript enabled.
2. Using keyboard navigation, Tab until you reach the "Skip to transcript" button.
3. Confirm the button stays hidden until focused, appears with correct spacing on focus, and moves focus to the transcript on activation.

Posted via collaboration with Claude Code

[kirsty-hames]

Works as expected thanks @swashbuck 👍