[llvm][docs] Add LLDB data formatters to DebuggingLLVM.rst

Add LLDB data formatters to the document about debugging LLVM.

Author: JDevlieghere

llvm/docs/DebuggingLLVM.rst

@@ -96,6 +96,16 @@ and each instruction printed by LLVM is suffixed with the file and line
 number of the instruction according to the debug information. Note that
 this requires debug information to be enabled (e.g. pass ``-g`` to Clang).
 
+LLDB Data Formatters
+===================
+
+A handful of `LLDB data formatters
+<https://lldb.llvm.org/resources/dataformatters.html>`__ are
+provided for some of the core LLVM libraries. To use them, execute the
+following (or add it to your ``~/.lldbinit``)::
+
+  command script import /path/to/lldbDataFormatters.py
+
 GDB pretty printers
 ===================