Write a initial guide

[jcornaz]

I create this issue issue to track the biggest missing pieces of documentation that are required to publish an "initial version" of the guide.

(Thanks @faassen for the list)

• How to define a body type (Static, Kinematic, Dynamic and Sensor)
• PhysicMaterial
• Collision detection
• 2d gotchaes (incl. rotation in 2d is around the z axis.) (this is more about bevy than heron)
• Change/Define velocity, acceleration, force and impulse
• How to acces Rapier directly (Document how to access rapier's RigidBody and RigidBodyBuilder methods #43)

[faassen]

Oh, and of course the various types of Body needs to be discussed! We need some kind of basic 3d example too but I definitely need help for that.

[jcornaz]

As there is already a form of documentation online (https://docs.rs/heron) I consider the "initial guide" to be already written.

It is by no means perfect or complete. But we can create more specific issues for what is missing or needs improvement.

[Hellzbellz123]

an example of using a sensor would be super helpful, something like a simple box that can move into 2 sensors triggering 2 separate things. ie sensor_a opening door_a while sensor_b opens door_b