What flow_text/7 and flow_across_boxes/4 managed to place.
overflow? is true when the text did not fit, and spill_text is what was
left over — pass it to another box, or another page.
Summary
Types
@type t() :: %Tincture.Layout.Box.FlowResult{ box_results: [Tincture.Typography.LayoutResult.t()], boxes_used: non_neg_integer(), overflow?: boolean(), spill_text: String.t() }