Improving navigation for GitHub Actions

GitHub has introduced a new navigation update for GitHub Actions, aimed at enhancing discoverability, accessibility, and scalability as developers automate their software development workflows. Since its launch in 2018, GitHub Actions has evolved significantly, prompting the need for a refined navigation system that supports the platform’s continued growth and new feature implementation. The sidebar has been renamed to "Actions" to better reflect the comprehensive management capabilities available, and a new navigation design has been integrated using GitHub's Primer design system, ensuring consistency across different viewports and improving accessibility. This update also enhances the hierarchy of reusable workflows, introduces entry points for Usage and Workflow files, and adds local navigation for easier wayfinding during workflow runs. These changes aim to future-proof GitHub Actions, making it a more resilient and user-friendly tool for developers.