Nested virtualization requirement

Author: kgremban

articles/iot-edge/tutorial-develop-for-linux.md

@@ -58,6 +58,7 @@ This tutorial teaches the development steps for Visual Studio Code. If you would
 A development machine:
 
 * You can use your own computer or a virtual machine, depending on your development preferences.
+  * Make sure that your development machine supports nested virtualization. This capability is necessary for running a container engine, which you install in the next section.
 * Most operating systems that can run a container engine can be used to develop IoT Edge modules for Linux devices. This tutorial uses a Windows computer, but points out known differences on MacOS or Linux. 
 * Install [Git](https://git-scm.com/), to pull module template packages later in this tutorial.  
 * [C# for Visual Studio Code (powered by OmniSharp) extension](https://marketplace.visualstudio.com/items?itemName=ms-vscode.csharp).

articles/iot-edge/tutorial-develop-for-windows.md

@@ -52,6 +52,7 @@ A development machine:
 
 * Windows 10 with 1809 update or newer.
 * You can use your own computer or a virtual machine, depending on your development preferences.
+  * Make sure that your development machine supports nested virtualization. This capability is necessary for running a container engine, which you install in the next section.
 * Install [Git](https://git-scm.com/). 
 
 An Azure IoT Edge device on Windows: