Document SpringJoint

[Jondolf]

Rapier has a SpringJoint for constraining the distance between two bodies, but it is not mentioned on the website. People often have to ask whether a joint like this exists or scramble through the API docs and source code to find it.

It should have usage documentation like the other joints. This currently applies to all versions of Rapier, including the Bevy plugin and JS bindings.

[MaxBittker]

have you gotten this joint to work @Jondolf ?

[Jondolf]

Sorry, I haven't actually tried it myself, I'm just aware that Rapier has it and seen other people using it or asking about it... I have my own physics engine and primarily use that 😅

I just made this issue as part of an effort to gather some missing pieces in Rapier's documentation (see my 9 other issues from the same day lol). I see you opened dimforge/rapier.js#268 though; I haven't used the JS bindings, but I don't think I've seen anyone have crashes using the joint on the Rust side

[MaxBittker]

I'll try on the rust side!