add ICPC Problem Archive

Author: wa008

README.md

@@ -247,3 +247,4 @@ But knowing the stuff will help you become better! :muscle:*
 - :link: [InterviewCake](https://www.interviewcake.com/)
 - :link: [At Coder](https://atcoder.jp/)
 - :link: [Codility](https://www.codility.com/)
+- :link: [ICPC Problem Archive](https://icpc.kattis.com/)