Adds deployment notifications

[pcothenet]

What

• Creates a GitHub deployment when the publish workflow is initiated
• Updates the status of the deployment at the end of the workflow
• This will trigger Slack notifications based on the Slack<>GitHub settings

Why

• Rely on GitHub<>Slack instead of rolling our own custom notifications. This lets us have different settings for different channels / users/
• Mirror how we notify of other applications

SDK Release Checklist

• Have you added an integration test for the changes?
• Have you built the gem locally and made queries against it successfully?
• Did you update the changelog?
• Did you bump the package version?
• For breaking changes, did you plan for the release of the new SDK versions and deploy the API to production?

[kleinjm]

👍