Add user Notebook on optical reconstruction

[chaozg]

• Smoothed Laplace prior
• Sample only selected set of x

After group meeting, we agreed that the smoothed Laplace distribution deserves a notebook of its own. So the current notebook will be split into two:

• The first #33 will focus on implementing and demonstrating the smoothed Laplace distribution,
• Potentially try smoothed laplace with with NUTS (small tree size) from both CUQIpy and CUQIpy-torch.
• The second will focus on the super-resolution problem. Proper cross-reference is expected.