chore: add minor code improvements to the typosquatting heuristic

[AmineRaouane]

Summary

some improvement for the typosquatting heuristic

Description of changes

• bash file to fetch the top downloaded packages in last month and store them in popular_packages.txt

Related issues

Checklist

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• I have tested my changes and verified they work as expected.

[art1f1c3R]

Looks good to me, ran it through shellcheck and all looks fine, ran it locally and worked with no errors.

[behnazh-w]

@AmineRaouane Could you please add a note in the README.md explaining why Macaron maintainers should run this script, where it should be executed from (the path), and include an example command for clarity?