[srujankaleru2007]

Description

Adds the GitHub Security Advisory card template with severity levels, advisory ID, affected/fixed package versions, and site branding.

Closes #279

How I Tested This

• npm run check — passed (0 errors).
• npm run test -- tests/templates/security-advisory.test.ts — passed (7 tests).
• npm run test -- tests/templates/render.test.ts -t github-security-advisory — passed (3 tests).
• Checked the GitHub editor preview and Download PNG.
• npm run test — 1,431 passed; 5 unrelated tests timed out and Vitest reported a worker-start error.

AI Assistance

Copilot SDK in VS Code assisted with implementation and tests.

Type of Change

• New template
• Tests

Screenshots

Attach the default template preview screenshot.

Checklist

• This PR targets dev
• I was assigned the linked issue
• npm run check passes
• npm run test passes
• Tested locally with npm run dev
• Screenshot attached for this visual change
• New template follows the Template Guidelines

[anurag629]

Thanks @srujankaleru2007, this works. Check, all 1464 tests and the build pass on top of dev, and the renders look right: each severity with its own pill color and readable text, an unknown severity (even constructor) falling back to High, a white background with a pale accent, long values, and blank fields with no stray separators.