PWA101(v2.0): rewrite PWA101 tutorial in SymPy

[shenvitor]

Previous version of PWA101 (v1.0) see here
In these tasks, we have the following.
Furthermore:

Original Tasks

Beta Give feedback

1. Generate p+gamma (one single virtual particle) from QRules #5
   📝 Docs +1
   
2. Write tutorial of p+gamma -> (N* -> eta p) pi (spinless) #2
   3 of 3
   Epic 📝 Docs +2
   
3. Extend example with N* spectrum that has spin (angular momenta) #3
   Epic 📝 Docs +2
   
4. Formulate kinematics variables symbolically with SymPy and AmpForm #36
   📝 Docs +1
   

Up-to-date Tasks

Beta Give feedback

1. pgamma virtual state particle and QRules
2. symbolics expression of amplitude A from the examples