add readme for posterity

README.md

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+# NewProject
+---
+A simple demonstration of how to include multiple cpp files in a single project, using cmake. 
+
+There are three strategies:
+1. direct declaration in the main, with the external source files identified in the cmakelist add_executables.
+2. explicit inclusion (`#include mysource.cpp`). In this case, they should not be added to the cmakelist.
+3. The "canonical" or "best practice" c++ approach: explicit inclusion of a header file (`#include mysource.h`) which declares all the classes and methods publicly accessible to main. Both the source and header must be added to cmakelist.
+
+Here is my main, with all three strategies implemented:
+
+![inclusions](img/inclusions.png)
+
+Here is the cmakelist:
+
+![](img/cmakelist.png)
+
+Note, that you'll have to specify your version of cmake in the `set`. 
+
+You can build this with this command: 
+
+```shell
+ cmake --build {your-project-path}/NewProject/cmake-build-debug --target NewProject -j 14
+```
+
+And when you run the compiled binary, you should see:
+
+![the output](img/output.png)