add comments

internal/lib/shoelace.go

@@ -21,6 +21,9 @@ type Point struct {
 	Y float64
 }
 
+/*
+Area computes the area of a polygon given its vertices using the shoelace formula.
+*/
 func Area(points []Point) float64 {
 	total := float64(0)
 	n := len(points)