Update CHANGELOG.md

Author: mmacklin

CHANGELOG.md

@@ -1,6 +1,6 @@
 # CHANGELOG
 
-## [0.9.0]
+## [0.9.0] - 2023-06-01
 
 - Add support for in-place modifications to vector, matrix, and struct types inside kernels (will warn during backward pass with `wp.verbose` if using gradients)
 - Add support for step-through VSCode debugging of kernel code with standalone LLVM compiler, see `wp.breakpoint()`, and `test_debug.py`