fix: Enable compilerOptions noImplicitReturns and noUnusedParameters to improve type safety

[tekener]

Hi, we are using your lib inside a typescript project having the following quite common compilerOptions enabled inside out tsconfig.json.

    "noImplicitReturns": true,
    "noUnusedParameters": true

This PR enabled this settings on your project as well because the code issues hiding in your code are letting our tsc fail as well. To enable it I fixed most of the underlying code issues. I added @ts-ignore to the PluginResult interface because I was too shy to remove the not used generic parameter O.

Thank you

[coveralls]

Pull Request Test Coverage Report for Build 8815466799

Details

• 5 of 5 (100.0%) changed or added relevant lines in 5 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.03%) to 95.521%

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Totals
Change from base Build 8804657404:	0.03%
Covered Lines:	3441
Relevant Lines:	3549

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💛 - Coveralls

[tekener]

Hi @jonluca, just kindly asking if you are creating a release for that.

[github-actions]

🎉 This PR is included in version 11.6.2 🎉

The release is available on:

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

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