Dispatching variadic arguments to dependencies with splats

It should be possible, when a variadic parameter receives multiple arguments, to call a dependency for each of those arguments:

This could look like:

```just
foo *args: (bar *args)
@bar arg:
  echo bar: {{arg}}
```

Which would have the effect of, for each value in `args`, call `bar` with that value:

```
$ just a b c d
bar: a
bar: b
bar: c
bar: d
```