chore: add submodule info to README (#113)

Added cli command to initialize and clone the submodules prior to opening xcode project

Closes #112

Author: Logikgate

README.md

@@ -2,14 +2,17 @@
 
 To start diving into the v8 iOS runtime make sure you have XCode and [Homebrew](https://brew.sh/) installed, and then run the following
 ```bash
+# Install CMake
+brew install cmake
+
 # Clone repo
 git clone https://github.com/NativeScript/ns-v8ios-runtime.git
 
-# Install CMake
-brew install cmake
+# Initialize and clone the submodules
+cd ns-v8ios-runtime
+git submodule update --init
 
 # Open the runtime in XCode
-cd ns-v8ios-runtime
 open v8ios.xcodeproj
 ```