Add solid fake for perpendicular flap tutorial

[NiklasVin]

I added a solid fake implemented in Python to the perpendicular flap tutorial, similar to the already existing fluid-fake.

[MakisH]

Is this ready for review? Don't forget to add it into the README of the tutorial. I can generate some of the plots when reviewing.

I will fix the markdownlint, it is failing also elsewhere.

[MakisH]

@NiklasVin please rebase/merge from develop, the markdownlint issue is now fixed.

[NiklasVin]

Is this ready for review? Don't forget to add it into the README of the tutorial. I can generate some of the plots when reviewing.

I will fix the markdownlint, it is failing also elsewhere.

Yes, now this should be ready for review.

[MakisH]

@NiklasVin can you please enable edits by maintainers? It's a checkbox on the right.