Release/4.0.0

[nim65s]

• Add laikago (#113)
• Add simplified double pendulum (#118)
• update simple humanoid (#120)
• update SDF loader & Cassie for pinocchio 2.9.2 (private) (#121)
• remove deprecated loaders
• setup tooling:
  • black
  • flake8
  • pre-commit + CI
• reformat for black / pre-commit

[nim65s]

(waiting a rebase on #121 )