1. Added a test that runs all notebooks in the examples folder to ensure that they run without error. This also included the addition ofnbmake to the test dependencies.

2. We agreed not to useJupytext for the time being, so I added annbstripout hook to the pre-commit. This refuses to commit notebooks until all meta data has been stripped.

3. Of course 1. and 2. can be removed if we later decide to useJupytext.

4. Addedexamples/two_normal.ipynb. Notebook builds up an example graph using two normal distributions. Notebook then attempts to solve by running sgd on$\lVert \nabla \mathcal{L} \rVert_2^2$. Notebook then demonstrates that the objective function can be easily changed and solves the problem using a custom objective function based up minimising KKT residuals.

5. Added some ruff ignores rules to examples folder. I think we probably don't care about these things missing in examples.

Closes#103.