docs: add missing README screenshots

[omribz156]

Summary

• Add README screenshots for Skills, Prompts, Test Generator, and Docs.
• Reuse the existing README image style and keep the text additions focused on the pictured pages.

Closes #54.

Verification

• Captured screenshots from local Vite UI with Microsoft Edge via Playwright CLI.
• npm run ui:build
• git diff --check

Note: npx prettier --check README.md still reports formatting differences, but the base README already reports the same check failure before this change. I left the broader file formatting untouched.nnCI note: GitHub Typecheck/Lint currently fail on the same unrelated ui/src/components/AppShell.tsx and ui/src/pages/PlaywrightDashboard.tsx errors seen on PR #97; UI Build and Docs passed for this PR.

This was prepared with Codex assistance and manually reviewed before opening.

[MyNameIsEdi]

Thank you