Update Release Notes

Added support for long long and unsigned long long compile-time constant evaluation, addressing issue microsoft#7952.

Author: AnastaZIuk

docs/ReleaseNotes.md

@@ -23,6 +23,7 @@ The included licenses apply to the following files:
 - Fixed regression: [#7508](https://github.com/microsoft/DirectXShaderCompiler/issues/7508) crash when calling `Load` with `status`.
 - Header file `dxcpix.h` was added to the release package.
 - Moved Linear Algebra (Cooperative Vector) DXIL Opcodes to experimental Shader Model 6.10
+- Added support for `long long` and `unsigned long long` compile-time constant evaluation, fixes [#7952](https://github.com/microsoft/DirectXShaderCompiler/issues/7952).
 
 ### Version 1.8.2505