doc: add link

jtr109 · jtr109 · commit d060a379b4b7 · 2021-05-13T08:40:10.000+08:00
diff --git a/maximum_points_you_can_obtain_from_cards/src/lib.rs b/maximum_points_you_can_obtain_from_cards/src/lib.rs
@@ -1,3 +1,7 @@
+/*!
+ * https://leetcode.com/explore/challenge/card/may-leetcoding-challenge-2021/599/week-2-may-8th-may-14th/3739/
+ */
+
 pub struct Solution {}
 
 impl Solution {
