Add vcpkg installation instructions (keystone-engine#449)

docs/COMPILE.md

@@ -5,6 +5,11 @@ To compile Keystone on Windows, see [COMPILE-WINDOWS.md](COMPILE-WINDOWS.md)
 
 To cross-compiling for Windows from Linux, see [COMPILE-WINDOWS-CROSS.md](COMPILE-WINDOWS-CROSS.md)
 
+Alternatively, you can build and install Keystone using [vcpkg](https://github.com/Microsoft/vcpkg/) dependency manager with a single command:
+ - vcpkg install keystone
+
+VCPGK supports to build Keystone on Windows, Linux and Macos, the Keystone port in vcpkg is kept up to date by Microsoft team members and community contributors.
+
 Learn more on how to code your own tools with our samples.
 
  - For C sample code, see code in directory samples/