feat: upgrade CI Node.js versions from 18/20 to 20/22

[Copilot]

Updates GitHub Actions workflow to test against Node.js 20 and 22 instead of 18 and 20.

Changes

• Updated .github/workflows/main.yml matrix to use Node.js ^20 and ^22

Original prompt

---

This section details on the original issue you should resolve

<issue_title>[feature] upgrade CI's Node.js version to 20 and 22</issue_title>
<issue_description>see PR: #508

it runs Node.js 18 and 20, needs to change to 20 and 22

[main / test (^18) (pull_request)](https://github.com/casbin/node-casbin/actions/runs/19271700681/job/55101420459?pr=508)
main / test (^18) (pull_request)Successful in 45s
[main / test (^20) (pull_request)](https://github.com/casbin/node-casbin/actions/runs/19271700681/job/55101420455?pr=508)
main / test (^20) (pull_request)Successful in 48s
```</issue_description>

## Comments on the Issue (you are @copilot in this section)

<comments>
</comments>

• Fixes [feature] upgrade CI's Node.js version to 20 and 22 #510

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[github-actions]

🎉 This PR is included in version 5.41.0 🎉

The release is available on:

• npm package (@latest dist-tag)
• GitHub release

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