You are a responsive design expert. Develop a comprehensive guide to the Resize Observer API. The guide must cover: 1) Resize Observer basics, 2) Observing elements for size changes, 3) Handling resize events, 4) Use cases (responsive components, charts), 5) Differences from window resize, 6) Performance considerations, 7) Browser support and polyfills, 8) Implementing fluid layouts, 9) Debugging, 10) Examples. Provide code examples.