Add features in readme

[streeve]

(and note unsupported models)

[streeve]

reminder to suggest language for this @pabloseleson

[pabloseleson]

Here is an option:

CabanaPD currently includes the following:

• Force models
  • Bond-based (pairwise): prototype microelastic brittle (PMB)
  • State-based (multibody): linear peridynamic solid (LPS)
• Mechanical response:
  • Elastic (no failure)
  • Brittle fracture
• Thermomechanics (bond-based only)
• Time integration
  • Velocity Verlet
• Pre-crack creation
• Particle boundary conditions

[streeve]

@pabloseleson update. Feel free to just push any other changes