[web] Mandel-Cryer benchmark conversion to jupyter notebook

This MR contains the 'Mandel-Cryer Effect' benchmark previously documented as a markdown file transformed into a jupyter notebook including the OGS simulation using ogs6py. The time stepping for hydraulic and mechanic equations was adapted to a total time period of 1.5 s in 150 10 timesteps of 0.01 s and the remaining steps in 0.1 s.

Total runtime is about 800 seconds. LB: Please note that I will disable notebooks with RUNTIME > 600 on regular MR pipelines (they will only run on master) in another MR.