feat: Create a pre-commit hook to force signed commits

[fantonangeli]

Description

Create a pre-commit hook to check if the commit is correctly signed, and if not, reject the local commit with a clear message.

Motivation

Developers can forget to sign their commits, or a new contributor may not be aware of this mandatory setting.
When we create a PR with a non-signed commit, the DCO CI will fail, and we need to rebase all the commits, resign them and force-push, which is a bit time-consuming.

Proposed Implementation

Create a pre-commit hook to check the current commit when git commit ... is executed

Definition of Done

• Implementation: Fully implemented according to the Serverless Workflow spec.
• Unit Tests: Comprehensive unit tests are included and passing.
• Integration Tests: Verified within the monorepo and target environments (Web/VS Code).
• Documentation: Updated README.md, ADRs, or official docs.
• Performance: No significant regression in editor responsiveness.
• Accessibility: UI changes comply with accessibility standards.