added bounds function and segline to intersect function

internal/geom/intersect.go

@@ -0,0 +1,11 @@
+package geom
+
+func SegLineIntersect(A, B, O, D Vec) (bool, float64) {
+	r := Sub(B, A)
+	den := Cross(r, D)
+	if NearlyZero(den) {
+		return false, 0
+	}
+	t := Cross(Sub(O, A), D) / den
+	return t > EPS && t < 1-EPS, t
+}