[ArtifactHub.io] GPG public key annotation added

[didierofrivia]

Part of the work needed for Kuadrant/helm-charts#18

This PR adds a new annotation in the Helm Chart.yaml meant for displaying the public key used for signing its chart packages. More info in https://artifacthub.io/docs/topics/annotations/helm/

[codecov-commenter]

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Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 61.54%. Comparing base (a92b462) to head (c0ca750).
Report is 6 commits behind head on main.

Additional details and impacted files

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  Coverage   61.54%   61.54%           
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  Files           2        2           
  Lines         788      788           
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  Misses        251      251           
  Partials       52       52           

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[guicassolato]

I've downloaded the key hosted at the URL myself and confirmed the fingerprint matches.

Thanks @didierofrivia