update README.md, add example code diff

Author: CC11001100

README.md

@@ -9,9 +9,9 @@ Golang中缺少三元表达式，就导致某些情况三元表达式一行就
 
 ```go
 if a % 2 == 0 {
-return "偶数"
+    return "偶数"
 } else {
-return "奇数"
+    return "奇数"
 }
 ```