Add guides for Tizen.UI

Author: JoonghyunCho

docs/extensions/tizenx/guides/overview.md

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+# Guides
+
+This section provides detailed tutorials, best practices, and code examples to help you master the specific libraries within the Tizen Extension ecosystem.
+
+## Tizen.UI
+
+The Tizen.UI guides focus on streamlining user interface development. Learn how to construct responsive, maintainable, and readable UI code.
+
+## TizenX.ZLog
+
+The TizenX.ZLog guides are dedicated to application diagnostics and logging.
+
+### Where to go next?
+
+Select a topic from the sidebar to dive deeper into a specific module. If you are new to the Tizen Extension Library, we recommend starting with the Tizen.UI Getting Started guide to see immediate visual results in your application.