Update READMEs

cpp/README.md

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+# Cpp
+
+```
+shaunrd0/klips/cpp/
+├── cmake       # Example of using cmake to build and organize larger projects
+├── datastructs # Collection of useful datastructures written in C++
+├── opengl      # Barebones opengl application written in C++ built with make
+├── README.md
+├── sdl         # Barebones sdl application written in C++ built with make
+└── sdl-cmake   # Barebones sdl application written in C++ built with cmake
+```
+
+
+In general, if a `CMakeLists.txt` is included in the project's root directory, 
+we can build the example with the following commands
+
+```
+mkdir build && cd build
+cmake .. && cmake --build .
+```
+
+
+If cmake is not being used in a project, it can be built with `g++` manually using
+the commands outlined in `*/.vscode/tasts.json`, or by using VSCode to open the example
+and running the build task.