Describe the bug
The three icon-only links in the header navigation (GitHub, Twitter/X, Slack) lack accessible names, causing WCAG 2.1 Level A violations:
Hyperlink has no link text, label or image with a text alternative

Why is this important?
When the purpose of a link is clear users can easily navigate links on the page without having to see the surrounding information for context.
To Reproduce
Steps to reproduce the behavior:
- Go to 'homepage'
- Run on IBM Accessibility Checker
- See violation report
Expected behavior
all three icon links have descriptive aria-label attributes that screen readers can announce.
Screenshots

Desktop (please complete the following information):
- OS: Window
- Browser: Edge
- Version: N/A
Smartphone (please complete the following information):
- Device: N/A
- OS: N/A
- Browser: N/A
- Version: N/A