data.contact.get(i) in mujoco-js / WASM leaks memory

### Intro

CC @yuvaltassa

I'm trying to create a realtime simulation with mujoco-js and want to implement audio for collisions, so I'd like to access the contact impulse. However, none of the expected methods to retrieve contact information seem to work correctly.

### My setup

- mujoco-js 0.0.7 / WASM (not sure what mujoco version that equates; ideally that'd be documented in the npm package README)
- Firefox 147.0.2 (x64)
- CachyOS

### What's happening? What did you expect?

Trying to retrieve contacts manually using `const contact = data.contact.get(i)` will leak a lot of memory and eventually something crashes. Doing `contact.delete()` does not help.

I'd expect it to not crash on heap growth failure.

### Steps for reproduction

This quickly runs out of memory:

```ts
//
// [...]
function eachFrame() {
mujoco.mj_step(model, data);
for(let i = 0; i < data.ncon; i++) {
const contact = data.contact.get(i);
contact.delete();
}
}
```

### Minimal model for reproduction

_No response_

### Code required for reproduction

_No response_

### Confirmations

- [x] I searched the [latest documentation](https://mujoco.readthedocs.io/en/latest/overview.html) thoroughly before posting.
- [x] I searched previous [Issues](https://github.com/google-deepmind/mujoco/issues) and [Discussions](https://github.com/google-deepmind/mujoco/discussions), I am certain this has not been raised before.