Highway-env

- Fix collision reward in parking env
- Minor update of documentation and workflows
- Minor update of example notebooks
- Update rendering logic

- fix vehicle order in occupancy grid obs
- fix broken seeding implementation
- support numpy types for discrete actions
- use Runge-Kutta 4 integration for dynamical continuous actions, making the dynamics make more stable
- use gymnasium rather than gym

Fixes https://github.com/eleurent/highway-env/issues/400

- Change the step / reset / render interfaces to match the new API of gym 0.26
- Drop support for gym <0.26

- fix a bug in generating discrete actions from continuous actions
- fix more bugs related to changes in gym's latest versions
- new intersection-env variant with continuous actions
- add longitudinal/lateral/angular offsets to the lane as part of the kinematics observation's features
- add more configurable options for reward function and termination conditions
- add configurable min/max speed for continuous actions
- bug fix for reward computation in the multi-agent setting
- add get_available_actions for MultiAgentAction
- fix various deprecation warnings
- add a multi-objective version of HighwayEnv

Huge thanks to contributors zerongxi, TibiGG, KexianShen, lorandcheng