This PR adds... <!-- A brief description of what your PR does -->

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- [ ] I've kept this PR as small as possible (~500 lines) by splitting it into PRs with manageable chunks of code
- [ ] I've requested reviews from 1 reviewer
- [ ] I've tested existing features (website scan, sitemap, custom flow) in both node index and cli
- [ ] I've synced this fork with GovTechSG repo
- [ ] I've added/updated unit tests
- [ ] I've added/updated any necessary dependencies in `package[-lock].json` `npm audit`, portable installation on GitHub Actions
