feat(developer): Add an Optional Parameter to `outs` for an Index

### Is your feature request related to a problem? Please describe.

Working with lists of marks, sometimes in an inline menu, I would like to reference just a single symbol in the list. A "list" is always a string in a store variable. The function `outs` can output the entire string (list), I think it is a good choice of function to be used to reference a list item by index.

### Describe the solution you'd like

As per:

```
store(ModifierList) '… … …'
⋮
… any(BaseLetters) + '@' > context outs(ModifierList, 3)
```

In other languages, this would be equivalent to ModifierList[2] .

### Describe alternatives you've considered

_No response_

### Related issues

_No response_

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