Add fallow to QA Tools

[BartWaardenburg]

Checklist:

• I've read and understood Contributing Guidelines.
• I've added the new resource at the end of its section.
• This resource is out there for a while, and actively maintained.
• This resource is popular enough and has at least a few hundred stars on GitHub.

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Adds fallow to QA Tools. fallow statically analyzes JavaScript and TypeScript projects for unused files, exports, and dependencies, plus duplication, circular dependencies, and complexity hotspots. Actively maintained, 380+ GitHub stars, 5 contributors, MIT licensed.

[gokaygurcan]

Thanks for the PR. Can you please read the contribution guidelines, and update the description accordingly? In the meantime, let's wait for CI to do its part so that we can get this in.

[BartWaardenburg]

Thanks for the quick review, @gokaygurcan! Just pushed an update that aligns the description with the contribution guidelines and fills out the PR template checklist. Let me know if anything else needs tweaking.