Add example data

[jpwgnr]

Fix issue #365

[chrbeckm]

I think it is better to save the generated data in a file. This way, the participants can use np.genfromtxt again. And the fit values are the same between implementation and solution.

rng = np.random.default_rng(seed=42)
x = rng.random(10)
y = 1.6 * x + 0.2 * rng.uniform(-1,1, len(x))
np.savetxt("daten.txt", np.column_stack([x, y]), header="x y")

[jpwgnr]

@chrbeckm What do you mean by "same between implementation and and solution"?
I fixed the solution correspondingly.

[chrbeckm]

I overlooked the seed, so I am wrong, the values will be the same.

[jpwgnr]

You like it better, this way?