Scripts should say what they do

[mauro3]

It would be helpful to add comment lines to each script's top to state:

• what part of each lecture they belong to
• what equation they solve
• what method they use

Bonus points for actually stating the equation.

I realize that some of that is encoded in the file name, but I cannot decode that.

For instance for https://github.com/eth-vaw-glaciology/course-101-0250-00/blob/main/scripts/l2_diffusion_1D.jl:

# Lecture 2.2a Parabolic PDEs - solve diffusion equation with explicit forward Euler step
#
# ∂C/∂t = D ∂²C/∂x²