Adding image to README.md

Author: ifilot

README.md

@@ -3,8 +3,7 @@
 [![windows-build](https://github.com/ifilot/opengl-cpp-course/actions/workflows/windows.yml/badge.svg)](https://github.com/ifilot/opengl-cpp-course/actions/workflows/windows.yml)
 [![linux-build](https://github.com/ifilot/opengl-cpp-course/actions/workflows/linux.yml/badge.svg)](https://github.com/ifilot/opengl-cpp-course/actions/workflows/linux.yml)
 
-**Update**
-The build instructions below now target MinGW-w64 (via MSYS2) instead of MSVC.
+![Screenshot of rotating cube](lesson02/images/rotating_cube.jpg)
 
 ## Purpose and expectations
 This repository contains the source code for the OpenGL C++ course. The course