[clang] [clang][doc][SYCL] Add SYCL driver and device library release notes to ReleaseNotes.md (PR #211949)

[Alexey Bader via cfe-commits]

================
@@ -493,6 +493,32 @@ features cannot lower the translation-unit ABI level;
 
 #### Improvements
 
+- SYCL compilations now default to `-std=c++17` when no explicit language
+  standard is specified. Standards below C++17 are rejected with a diagnostic.
+
+- Clang now assumes the default target for SYCL device compilation is 64-bit
+  SPIR-V and diagnoses if a non-supporting target is specified on the command
+  line. (#GH167358)
+
+- The SYCL runtime shared library has been renamed from `libsycl.so` to
+  `libLLVMSYCL.so` to align with LLVM naming conventions.
+
+- SYCL header include paths are now added automatically for both host and
+  device compilations.
----------------
bader wrote:

```suggestion
- In SYCL mode, the compiler driver automatically provides the necessary SYCL header include paths to both the host and device compilers.
```
\+ word wrapping.

https://github.com/llvm/llvm-project/pull/211949