RFC: Load SwiftLint version in the Package Description

[iangmaia]

This PR is a simple experiment on loading the right SwiftLint version defined in .swiftlint.yml in the Package Description.
I have refrained from using a proper YAML parser to keep it simple, so I just load the file and parse it as a string.

I don't have many ideas on sharing this code to use in other repos, but perhaps it also isn't a big deal to replicate it as needed.

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• I have considered if this change warrants release notes and have added them to the appropriate section in the CHANGELOG.md if necessary.

[dangermattic]

	1 Warning
⚠️	Package.swift was changed without updating its corresponding Package.resolved. Please resolve the Swift packages in Xcode.

Generated by 🚫 Danger

[mokagio]

Looking good. I tried changing the version locally and it did indeed fetch the new one. 👍