develop better heuristics for appending `| print`

The current everistics doesn't catch multiline string definitions

```nu
export def ends-with-definition [
    condition: string
]: nothing -> bool {
    $condition =~ '(;|null|(?>[^\r\n]*\b(let|def|use)\b.*[^\r\n;]*))$'
}
"let a = r#'\"High up in the mountains, a Snake crawled and lay in a damp gorge, coiled
    into a knot, staring out at the sea.'#" | ends-with-definition $in
```