added stl.natvis to stl

README.md

@@ -362,6 +362,20 @@ The `SKIPPED` result code indicates that a given test was explicitly skipped by
 * taking a very long time to run
 * failing or passing for the incorrect reason
 
+# Editing And Testing The Debugger Visualizer
+
+### Modify The Visualizer
+
+To modify how components are visualized in the debugger edit the file `stl\debugger\STL.natvis`. For more information on
+how to modify this file check the [natvis documentation][].
+
+### Test Your Changes
+
+You can add the natvis file to any Visual Studio C++ project if you right click your project > Add > Existing Item and
+select the STL.natvis file. After doing this you should be able to see your changes in a Visual Studio debugging
+session.
+
+
 # Block Diagram
 
 The STL is built atop other compiler support libraries that ship with Windows and Visual Studio, like the UCRT,
@@ -423,3 +437,4 @@ SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 [opencode@microsoft.com]: mailto:opencode@microsoft.com
 [redistributables]: https://support.microsoft.com/en-us/help/2977003/the-latest-supported-visual-c-downloads
 [vcpkg]: https://github.com/microsoft/vcpkg
+[natvis documentation]: https://docs.microsoft.com/en-us/visualstudio/debugger/create-custom-views-of-native-objects