bunfig docs are incomplete

### What is the type of issue?

_No response_

### What is the issue?

I found that bunfig supports the following undocumented setting.
```
[target]
default = "node"
```

Now I wonder if there are other undocumented things, for example to specify the outdir in bunfig.

### Where did you find it?

https://bun.com/docs/runtime/bunfig