docs(blog): introduce the Atmos product roadmap

Add a blog post announcing the new public product roadmap page, highlighting:
- Featured improvements like Dev Containers, Cloud Auth, and Workflows
- Major initiatives including Terragrunt parity and documentation overhaul
- Overall progress tracking across all milestones
- How to get involved and provide feedback

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: osterman

website/blog/2025-12-23-product-roadmap.mdx

@@ -0,0 +1,31 @@
+---
+slug: product-roadmap
+title: "Introducing the Atmos Product Roadmap"
+authors:
+  - osterman
+tags:
+  - feature
+  - documentation
+date: 2025-12-23T00:00:00.000Z
+---
+
+We're sharing the [Atmos Product Roadmap](/roadmap)—a transparent view of where we've been, where we're headed, and what's coming next. Infrastructure teams evaluating Atmos often ask *"What's the long-term vision?"* The roadmap answers that question openly.
+
+<!--truncate-->
+
+## What's on the Roadmap
+
+The page is organized around a visual quarter timeline from Q1 2025 through Q2 2026. Featured improvement cards highlight major capabilities—click any card to see details, documentation links, and associated PRs. Below that, expandable initiative cards group milestones by theme, with an animated progress bar tracking overall completion.
+
+## Get Involved
+
+The roadmap isn't just for viewing. Here's how you can shape it:
+
+- **Star issues** on GitHub that matter to you
+- **Open feature requests** for capabilities you need
+- **Contribute directly** to any roadmap item
+
+## Learn More
+
+- [View the Roadmap](/roadmap) - Browse everything we've shipped and what's planned
+- [GitHub Issues](https://github.com/cloudposse/atmos/issues) - Vote on features or request new ones