Write tests

[ajbozarth]

Due to my own short-comings, I did not include tests. The original copier template had an option to include the testing framework that I did not leverage (similarly I also did not include the server component in my initial POC and had to manually add it in later). We should be able to add tests by leveraging the template, through it will take some work since the copier yml no longer exists to run copier upgrade

If we hope for this extension's use to expand beyond just Qiskit Code Assistant, adding tests would be important to future stability.