Function parse_grid_template_areas 

pub fn parse_grid_template_areas(input: &str) -> Result<GridTemplateAreas, ()>

Parse grid-template-areas CSS value.

Accepts quoted row strings like: "header header header" "sidebar main aside" "footer footer footer"

Returns a GridTemplateAreas with deduplicated named areas and their computed row/column line boundaries (1-based, as taffy expects).