Update tools.mdx

Adding alt text to toolkit cover image

content/guides/accessibility/tools.mdx

@@ -16,7 +16,7 @@ When testing contrast be wary of tools that use color pickers. The picked color
 This Figma library includes annotations to use on your designs prior to developer hand off. These annotations let you document semantic structure, make visuals and interactions accessible
 Annotate design system components, outline DOM order, and work better together. It is active by default in all new Figma files, and can also be activated [manually](https://accessibility-playbook.github.com/enabling-a11y-design-toolkit-library-in-figma) if needed.
 
-<img src="https://github.com/user-attachments/assets/4816f0d0-0a00-40d6-bc69-c1d988b82092"  alt="">
+<img src="https://github.com/user-attachments/assets/4816f0d0-0a00-40d6-bc69-c1d988b82092"  alt="GitHub Annotation Toolkit cover image, featuring an annotated GitHub.com homepage and a design checkpoints tool overlaying some abstract branded GitHub-y key art. A badge in the top right corner says Beta.">
 
 ### [A11y - Focus Order plugin](https://www.figma.com/community/plugin/731310036968334777/A11y---Focus-Orderer)