Support `ripser++` as a backend for Vietoris–Rips complex calculations

[Pseudomanifold]

• Some previous benchmarks by @crisbodnar: https://colab.research.google.com/drive/1CbLnKu4v964Gxb2FDsxp1kgPwe0pOKpl?usp=sharing
• Suggestion for integration: use str parameter for VietorisRipsComplex
• Add as optional dependency