readme: Added CMake build instructions

README.md

@@ -5,7 +5,16 @@ Traditional techniques account for network transmission time by adding delay to
 
 For more information about the history of GGPO, check out http://ggpo.net/
 
-This repository contains the code, documentation, and sample application for the Windows version of the SDK (requires Visual Studio 2019).
+This repository contains the code, documentation, and sample applications for the SDK.
+
+## Building
+Building GGPO is currently only available on Windows, however efforts are being made to port it to other platforms. To get started, clone the repository using either git or svn:
+```git clone https://github.com/pond3r/ggpo.git```
+**OR**
+```svn checkout https://github.com/pond3r/ggpo```
+
+### Windows 
+On windows, it's recommended to use Visual Studio 2019 and cmake-gui (which can be downloaded [here]([https://cmake.org/download/])). Once everything has been setup, open cmake-gui and select the root of the repository under ```Where is the source code:``` followed by the build folder under ```Where to build the binaries:```. Next, hit ```Configure``` and change any options that appear in the main window before hitting ```Generate``` which will generate the VS2019 solution. Once the solution has been generated, hit ```Open Project``` and build with the appropriate settings (Debug/Release). The built binaries can then be found where they were configured to be built.
 
 ## Licensing
 GGPO is available under The MIT License. This means GGPO is free for commercial and non-commercial use. Attribution is not required, but appreciated.