add: leetcode 0520 solution

leetcode/0520.Detect-Capital/520.Detect Capital.go

@@ -0,0 +1,13 @@
+package leetcode
+
+import "strings"
+
+func detectCapitalUse(word string) bool {
+	wLower := strings.ToLower(word)
+	wUpper := strings.ToUpper(word)
+	wCaptial := strings.ToUpper(string(word[0])) + strings.ToLower(string(word[1:]))
+	if wCaptial == word || wLower == word || wUpper == word {
+		return true
+	}
+	return false
+}