Add rendered notebooks to the docs

[timothy-nunn]

The notebooks are currently stored in our repository in a run state. I think our notebooks should not contain any non-cell data such as plots from running on one of our machines. This also means they can become out-of-sync with PROCESS (e.g. outputs and plots) until we decide to push a newly run version up.

We should render our examples in the docs similar to https://ukaea.github.io/PyVMCON/example.html
After this, we should keep only clean notebooks in our repository (its possible ruff can be used for this).