readme: fix readme to mention c++17 support

README.md

@@ -434,7 +434,10 @@ On MacOS
 - AppleClang 11.0
 
 On Windows
-- Visual Studio 2017
+- Visual Studio 2019
+
+  You might still build using 2017, but its c++17 support is incomplete so
+  we might drop its support as soon as we use an unsupported language feature.
 
 Other compilers or later versions may work, but they are not tested.
 
@@ -497,7 +500,7 @@ The script requires Chromium's
 
 ### Usage
 
-The internals of the library use C++11 features, and are exposed via both a C
+The internals of the library use C++17 features, and are exposed via both a C
 and C++ API.
 
 In order to use the library from an application, the include path should point