v0.3.0

d5fee3a feat: add helper sensitivities and adjoint functions to method trait (#101)
29a29ae feat: adjoint equations (#99)
cfacee1 feat: checkpointing and solver-specific state (#97)
176f856 feat: solvers support reverse time (for internal use only) (#93)
b7f0589 refactor: solve and solve_dense use a dense matrix type for state return (#90)
8d19b87 feat(diffsl): update & enable cranelift backend (#86)
d558868 perf(bdf, sdirk): jacobian update controller (#85)