Accessibility issues from Jan 2024 review

[robertknight]

This issue covers resolving accessibility issues identified in the January 2024 review by OCAD that affect the client.

• Notebook modal dialog is not properly represented as a dialog #6158
• Incorrect use of aria-pressed for sidebar collapse/expand button #6163
• aria-pressed not used for "Show highlights" button #6166
• Annotation/Reply body text areas accessibility improvements #6179
• <article> label is the same for every annotation by the same author #6185
• Add status message confirming when a highlight is created #6188
• Indicate links that open in new tabs to assistive technologies #6193
• Improve close button label specificity #6194

[acelaya]

The main tasks have been completed, and there are individual issues for the pending tasks, so I'm going to go ahead and close this.