aria_content_in_landmark flags skip links as content outside landmark

[stjordan]

Describe the bug
The aria_content_in_landmark rule flags skip links as content outside a landmark. Skip links are not content and adding a needless landmark worsens the screen reader experience.

To Reproduce
Steps to reproduce the behavior:

1. Go to https://designsystem.digital.gov/ or many other websites, such as whitehouse.gov
2. Run the Accessibility Assessment from Chrome Dev Tools
3. Observe that /document[1] /link[1] is flagged for being outside a landmark

Expected behavior
/document[1] /link[1] is not flagged for being outside a landmark. Perhaps the heuristic is to exclude the link from this rule if it is the first link in the DOM and its target is the main landmark.

Desktop (please complete the following information):

• OS: macOS 14.6
• Browser: chrome
• Version: 131.0.6778.139

Definition of Done

• Design artifacts reviewed
• Work item implemented
• Automated test case created (when applicable)
• Unit test completed
• Run Checker (when applicable)
• Manual and Screen Reader Testing (when applicable)
• Video recording of user experience walkthrough (if impact to UX)
• PR created