Add friction/Contact Material example

[Glavin001]

Friction (#64)

• Inspired by: https://pmndrs.github.io/cannon-es/examples/friction
  • Source: https://github.com/pmndrs/cannon-es/blob/6f11e268d5e196f7f4f5908dbf60ae6365bd6ab6/examples/friction.html
  • Special thanks to https://github.com/pmndrs/use-cannon/pull/297
• [x] Finalize/agree on the API
  • Material name: useContactMaterial("string1", "string2", { ... })
  • Material Options object: useContactMaterial({ name: "string1" }, { name: "string2" }, { ... })
    • [x] Update MaterialOptions type to include name
  • [x] Demo shows the cleanup works / can update the ContactMaterial properties
• [x] Add useContactMaterial docs to README

Demo

https://use-cannon-git-fork-glavin001-feat-contact-material-pmndrs.vercel.app/#/demo/Friction

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[Glavin001]

@bjornstar : Ready for code review. Thanks!