Finalize changelog for 1.3.0 release.

Author: brycelelbach

docs/releases/changelog.md

@@ -1,5 +1,30 @@
 # Changelog
 
+## libcu++ 1.3.0 (CUDA Toolkit 11.2)
+
+libcu++ 1.3.0 is a major release included in the CUDA 11.2 toolkit. It supports
+ABI version 2 and 3. It adds `<tuple>` and `pair`, although they are not
+supported with NVCC + MSVC. It also adds documentation.
+
+### New Features
+
+- `<cuda/std/tuple>`/`cuda::std::tuple`.
+  - Not supported with NVCC + MSVC.
+- `<cuda/std/utility>`/`cuda::std::pair`.
+  - Not supported with NVCC + MSVC.
+
+### Other Enhancements
+
+- [Documentation](https://nvidia.github.io/libcudacxx).
+
+### Bug Fixes
+
+- #21: Disable `__builtin_is_constant_evaluated` usage with NVCC in C++11 mode
+    because it's broken.
+- #25: Fix some declarations/definitions in `__threading_support` which have
+    inconsistent qualifiers.
+  Thanks to Gonzalo Brito Gadeschi for this contribution.
+
 ## libcu++ 1.2.0 (CUDA Toolkit 11.1)
 
 TODO