Add a github workflow to automatically publish a new version of the gem

[Aelysya]

Description

As a developer, I want to add a workflow to automatically publish a new version of the psdk-cli gem, so that I don't have to do everything manually.

Acceptance Criteria

• The workflow is triggered manually from github and automatically manages the gem publishing.
• A notification is sent to the project-notification channel on discord when the worklow successfully ends.
• The workflow checks the version of the repository against the currently public one, and stops with an error if they're the same or if the repository's is older.