[Suggestion]: Docs: explain the first example

[ocramz]

Suggestion / Feature Request

The first example in the README could use some introduction to make sense of the interface, e.g :

• What are the parameters b and s of zeroout_intervention_fn ?
• "3rd position" of what?
• is the intervention field of the configuration dict always a binary function?

def zeroout_intervention_fn(b, s): 
    b[:,3] = 0. # 3rd position
    return b

pv_model = pv.IntervenableModel({
    "component": "model.layers[15].mlp.output", # string access
    "intervention": zeroout_intervention_fn}, model=model)