add trusted publishers

[mensfeld]

No description provided.

[Copilot]

Pull Request Overview

This PR removes local gem signing in favor of trusted publishers and adds a GitHub Actions workflow to publish the gem automatically.

• Remove gem.cert_chain and signing key logic from the gemspec
• Delete the local certificate file
• Update the changelog to note the move to trusted publishers
• Add a push.yml workflow to automatically release tagged versions

Reviewed Changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 2 comments.

File	Description
rdkafka.gemspec	Removed cert_chain and signing_key configuration
certs/cert.pem	Deleted the local certificate file
CHANGELOG.md	Added changelog entry for migrating to trusted publishers
.github/workflows/push.yml	Introduced a new workflow to publish gems on tag pushes

Comments suppressed due to low confidence (1)

.github/workflows/push.yml:12

• [nitpick] The job id push is very generic; renaming it to something like release-gem or publish would make its purpose clearer.

  push: