Add release note

Author: mysterymath

lld/docs/ReleaseNotes.rst

@@ -40,6 +40,9 @@ ELF Improvements
   * ``R_X86_64_CODE_4_GOTTPOFF`` (`#116634 <https://github.com/llvm/llvm-project/pull/116634>`_)
   * ``R_X86_64_CODE_4_GOTPC32_TLSDESC`` (`#116909 <https://github.com/llvm/llvm-project/pull/116909>`_)
   * ``R_X86_64_CODE_6_GOTTPOFF``  (`#117675 <https://github.com/llvm/llvm-project/pull/117675>`_)
+* ``--why-live=<glob>`` prints for each symbol matching ``<glob>`` a chain of
+  items that kept it live during garbage collection. This is inspired by the
+  Mach-O LLD feature of the same name.
 
 Breaking changes
 ----------------