Update CHANGELOG.md - Version 0.2.0

Author: aafulei

CHANGELOG.md

@@ -1,5 +1,47 @@
 # Changelog
 
+## [0.2.0]() - 2025-05-14
+
+**Integrated with Doxygen for source code documentation.**
+
+### Added
+
+- Source code:
+    - Doxygen-style comments
+- Testing:
+    - `test.sh`
+- Build system:
+    - Full support of `release` and `debug` branches
+    - `make test`
+    - `make install/uninstall`
+    - `make show-os`
+    - `make show-compiler`
+- Automation:
+    - GitHub Actions:
+        - `build.yml` for automatic building workflow on latest macOS and Ubuntu
+        - `test.yml` for automatic testing workflow on latest macOS and Ubuntu
+        - `check.yml` for automatic code format check workflow on latest macOS
+- Project website:
+    - MkDocs with the Material theme:
+        - Getting Start section
+        - Testing section
+        - Build System section
+- Code reference:
+    - Doxygen:
+        - `Doxyfile` for docs generation
+        - `DoxygenLayout.xml` for website layout
+- Assets:
+    - `.svg` images for CppToday logo and icon
+    - `.css` files to customize website appearance
+- Project information:
+    - `LICENSE` for software license (MIT)
+    - `.gitignore`
+        - Ignore `site/` and `venv/`
+        - Ignore doxygen, original, backup files
+    - `CHANGELOG.md` for Changelog:
+        - Version 0.2.0
+        - Version 0.1.0
+
 ## 0.1.0
 
 **Initial release of the `today` program.**