added vendor

vendor/github.com/andybalholm/cascadia/specificity.go

@@ -0,0 +1,26 @@
+package cascadia
+
+// Specificity is the CSS specificity as defined in
+// https://www.w3.org/TR/selectors/#specificity-rules
+// with the convention Specificity = [A,B,C].
+type Specificity [3]int
+
+// returns `true` if s < other (strictly), false otherwise
+func (s Specificity) Less(other Specificity) bool {
+	for i := range s {
+		if s[i] < other[i] {
+			return true
+		}
+		if s[i] > other[i] {
+			return false
+		}
+	}
+	return false
+}
+
+func (s Specificity) Add(other Specificity) Specificity {
+	for i, sp := range other {
+		s[i] += sp
+	}
+	return s
+}