docs: add vcpkg installation instructions (#252)

Author: gabrieljablonski

INSTALL.md

@@ -11,3 +11,17 @@
 2. Add `./lib/asio/asio/include`, `./lib/websocketpp` and `./lib/rapidjson/include` to headers search path.
 3. Include all files under `./src` in your project, add `sio_client.cpp`,`sio_socket.cpp`,`internal/sio_client_impl.cpp`, `internal/sio_packet.cpp` to source list.
 4. Include `sio_client.h` in your client code where you want to use it.
+
+### With vcpkg
+
+You can download and install the Socket.IO C++ client using the [vcpkg](https://github.com/Microsoft/vcpkg) dependency manager:
+
+```bash
+git clone https://github.com/Microsoft/vcpkg.git
+cd vcpkg
+./bootstrap-vcpkg.sh
+./vcpkg integrate install
+vcpkg install socket-io-client
+```
+
+The Socket.IO client port in vcpkg is kept up to date by Microsoft team members and community contributors. If the version is out of date, please [create an issue or pull request](https://github.com/Microsoft/vcpkg) on the vcpkg repository.

README.md

@@ -44,6 +44,7 @@ Note: Only the WebSocket transport is currently implemented (no fallback to HTTP
 
 * [With CMAKE](./INSTALL.md#with-cmake)
 * [Without CMAKE](./INSTALL.md#without-cmake)
+* [With VCPKG](./INSTALL.md#with-vcpkg)
 * [iOS and OS X](./INSTALL_IOS.md)
  * Option 1: Cocoapods
  * Option 2: Create a static library