[Release] Prepare 1.2.0

[sonukapoor]

Summary

Prepare the 1.2.0 release.

Included Since 1.1.1

• reusable first-party GitHub Action via action.yml
• official workflow integration guidance for scripts, hooks, CI, and scheduled advisory DB refreshes
• follow-up reliability fix removing built-in npm cache setup from the reusable action
• multi-column README table of contents and additional Action usage examples

Versioning

• bump package version from 1.1.1 to 1.2.0
• add the 1.2.0 changelog entry

Verification

• npm test
• npm run build