Add usage examples

[tdowrick]

There are some suggested usage scenarios outlined in the README.md. We should have some examples of how to configure/build in each case.

• C++ library in C++ command line interfaces.
• C++ library in a C++ user interface, using Qt, or QML.
• C++ library in a Python module, or perhaps a Python GUI, where the Python is developed separately, outside of this project.
• C++ library in an environment such as Unity, developed outside of this project.

e.g. for the simplest use case 'Command Line Apps'

# Build
git clone https://github.com/MattClarkson/CMakeCatchTemplate 
mkdir build 
cd build 
cmake ../CMakeCatchTemplate 
make 

# Run tests & code example
cd MYPROJECT-build/bin 
./mpBasicTest 
./mpCommandLineArgsTest sample_argument 
./mpMyFirstApp 

[tdowrick]

I will add these on my forked repo.

[tdowrick]

Closing as we have examples in GitHub Actions