Updated README regarding Visual Studio support

Author: yhirose

README.md

@@ -787,6 +787,8 @@ Include `httplib.h` before `Windows.h` or include `Windows.h` by defining `WIN32
 #include <httplib.h>
 ```
 
+Note: cpp-httplib officially supports only the latest Visual Studio. It might work with former versions of Visual Studio, but I can't no longer verify it. Pull requests are always welcome for the older Visual Sutudio unless it breaks the C++11 conformance.
+
 Note: Windows 8 or lower and Cygwin on Windows are not supported.
 
 License