Accessibility Improvements

Description

This PR makes the following accessibility improvements to the dashboard:

• It adds a skip link in order to satisfy WCAG Success Criterion 2.4.1 Bypass Blocks.
  • It's worth noting that the skip link styling intentionally utilizes Tailwind's outline classes rather than ring classes because the ring classes rely on box shadows, and box shadows are removed in Windows High Contrast Mode (which would result in focus indicators no longer being visible in WHCM).
• It adds sr-only <h1> elements to each of the 4 settings pages, so as to ensure that heading levels aren't skipped and each of the settings pages provides a main heading to screen readers.
• It adds an ARIA label to the settings sub-navigation menu so as to provide better context for screen reader users.

Screenshots

Skip Link -- Light Mode

Skip Link -- Dark Mode

VoiceOver Headings List -- Profile Settings Page

VoiceOver Headings List -- Password Settings Page

VoiceOver Headings List -- Two-Factor Authentication Page

VoiceOver Headings List -- Appearance Settings Page

Settings Navigation ARIA Label

Screencast of Skip Link in Action

Note: As demonstrated in this screencast, the skip link, when used, will skip repetitive navigation (e.g., the sidebar navigation) and move keyboard focus to the main content of the page. It will also respect reduced motion preferences that are set at the OS level (i.e., the transition will be removed if the user has reduced motion preferences set).