add a development plan

[hstojic]

link to in contribution guidelines, what is in scope etc

[hstojic]

• basics:
  • ground truth models
• environment models:
  • probabilistic modelling with GPflow support
  • efficient and consistent sampling with prob models
  • reward modellnig
  • return modelling
• decision time planning
  • state conditioned
  • path integral
  • extend horizon with return modelling
  • MCTS
• background planning
  • ?
• other types of planning
  • PILCO style?
  • SVE?
• POMDP support
• offline RL support
• constrained, risk aversion & other directions