NiftyPAD v2.0.0 beta

• add image_to_parametric_files (uses image_to_parametric) (#6)
• add (automatic) mask file support
• add list of models support
• change user_inputs (#6)
• add mrtm_ppet
• generalise the input args for Ref interpolation
• enable coffee break and weights in graphic models
  • add various interpolations for filling coffee break
  • add frame time conversion for coffee break
  • exclude time points in coffee break for graphic models
• fix nibabel reads
• misc bugfixes
• update docs
  • add diagram
  • add citation info
• misc code linting & tidy
• misc build/framework/CI/tests updates
  • use release bot
  • support Py3.11, drop Py3.6
  • migrate from setup.cfg => pyproject.toml
  • exclude images from package data
  • fix/update workflows
  • update pre-commit