add visual for neural network before composing it in keras

[psteinb]

as recommended by our learners during the 20210622 trial teaching, a visual representation will help people build a concept before punching in the code

[colinsauze]

It would be really useful if there's a way we an visualise the network we build in the "Create the neural network" exercise. From a quick google search, Keras has a built in model plotting tool - https://keras.io/api/utils/model_plotting_utils/

[bpmweel]

In our recent workshop I just pasted the image I used in my introductory slides in a markdown cell, this worked very well.

Indeed perhaps doing the visualization using the model plot would show that the architecture indeed matches

[bpmweel]

Closing in favour of #125