Trajectory gallery: let's discuss

[paquiteau]

From the discussions in #77, #105, #106, #113, and more, It seems that a better display of the trajectories in MRI-NUFFT documentation (building on top of the amazing work of @Daval-G ). As more and more trajectories are added, the question of their discoverability is also at hand.

Technically speaking, the Sphinx Gallery seems to be a good base to work on; an inspiring example can be from matplotlib itself (https://matplotlib.org/stable/gallery/index.html)! Using sections and tagging may be a good idea as well.

Writing a script for each trajectory may be too repetitive, so maybe some templating system can be used (one solution may be to describe the trajectory in .json/.yaml and generate a .py file from it with jinja ). Also, some extra CI configuration could be helpful.

However, it is necessary first to discuss exactly what we want to display for each trajectory.