fix(package): correct the Node engine floor

[GSTJ]

Summary

The package now declares Node 14 as its minimum runtime, matching the JavaScript in the published build.

Details

• The emitted build uses nullish coalescing, which Node 12 fails to parse.
• The Node 14 engine floor lets strict package managers reject incompatible installs before runtime.

Testing steps

1. From the root of the checked-out repository, run:

   pnpm install --frozen-lockfile
   pnpm run build
   npm pack

2. From the same directory, run:

   docker run --rm -v "$PWD:/package:ro" node:12-alpine sh -lc 'mkdir /app && cd /app && npm_config_engine_strict=true npm install /package/eslint-plugin-safe-jsx-1.3.7.tgz'

   The install should stop with an unsupported engine error.

3. Run:

   docker run --rm -v "$PWD:/package:ro" node:14-alpine sh -lc 'mkdir /app && cd /app && npm_config_engine_strict=true npm install --no-save /package/eslint-plugin-safe-jsx-1.3.7.tgz >/dev/null && node -e "console.log(require(\"eslint-plugin-safe-jsx\").meta)"'

   The command should print the plugin name and version.

4. Run the repository checks:

   pnpm run lint
   pnpm run format
   pnpm run typecheck
   pnpm run test
   pnpm run build
   pnpm run changelog:check
   pnpm audit --audit-level low

[github-actions]

🎉 Congratulations on making your first pull request in '@gstj/safe-jsx'! We appreciate your contribution and will review it as soon as possible. Thank you for helping us make this project better.

[GSTJ]

Proof from 742b7c5: Node 12 rejects the package under strict engine checks, and Node 14 runs the rule through ESLint. The second image has the full local suite.