update README.md to add prerequisites for each type of module (#457)

* update README.md to add prerequisites for each type of module

* Update header size

* Update README.md

* Update README.md

README.md

@@ -29,7 +29,9 @@
 
 ## Prerequisites
 
+You need to install prerequisites below to make Azure IoT Edge extension work: 
 - [Docker](https://www.docker.com/)
+- [Python](https://www.python.org/downloads/) and [Pip](https://pip.pypa.io/en/stable/installing/#installation)
 - [iotedgehubdev](https://pypi.org/project/iotedgehubdev/)
     ```
     pip install --upgrade iotedgehubdev
@@ -37,6 +39,33 @@
 - It's also recommended to install [Docker Support for Visual Studio Code](https://marketplace.visualstudio.com/items?itemName=PeterJausovec.vscode-docker) to manage your IoT Edge Docker images, containers and registries. 
 - The current user must have permissions to manage Docker. By default this is not the case on Linux, check the [FAQ section](#FAQ) to avoid `permission denied` errors.
 
+To develop IoT Edge modules you also need to install following prerequisites for specific language:
+  #### C# module prerequisites
+  - [.NET Core 2.1 SDK](https://www.microsoft.com/net/download)
+  - [C# for Visual Studio Code (powered by OmniSharp) extension](https://marketplace.visualstudio.com/items?itemName=ms-vscode.csharp)
+
+  #### C# Functions on IoT Edge prerequisites
+  - [.NET Core 2.1 SDK](https://www.microsoft.com/net/download)
+  - [C# for Visual Studio Code (powered by OmniSharp) extension](https://marketplace.visualstudio.com/items?itemName=ms-vscode.csharp)
+
+  #### Python module prerequisites
+  - [Python](https://www.python.org/downloads/) and [Pip](https://pip.pypa.io/en/stable/installing/#installation)
+  - [Git](https://git-scm.com/downloads) for cloning module template from GitHub
+  - [Python extension](https://marketplace.visualstudio.com/items?itemName=ms-python.python) for Visual Studio Code
+
+  #### Node.js module prerequisites
+  - [Node.js and npm](https://nodejs.org/)
+  - [Yeoman](https://yeoman.io/)
+
+  #### Java module prerequisites
+  - [Java SE Development Kit](https://aka.ms/azure-jdks), and [set the JAVA_HOME environment variable](https://docs.oracle.com/cd/E19182-01/820-7851/inst_cli_jdk_javahome_t/) to point to your JDK installation.
+  - [Maven](https://maven.apache.org/)
+  - [Java Extension Pack](https://marketplace.visualstudio.com/items?itemName=vscjava.vscode-java-pack) for Visual Studio Code.
+
+  #### C module prerequisites
+  - [Git](https://git-scm.com/downloads) for cloning module template from GitHub
+  - [C/C++ extension](https://marketplace.visualstudio.com/items?itemName=ms-vscode.cpptools) for Visual Studio Code.
+
 ## Quickstart
 Click the links below to learn how to develop, debug and deploy IoT Edge modules.