jigsawpuzzle2: GCPC 2018 problem is missing

[ghamerly]

What's wrong?

The problem jigsawpuzzle from GCPC 2018 was never installed. There is a name clash with an existing problem, so we will call the GCPC version jigsawpuzzle2.

The source is here: https://github.com/mzuenni/kattis-export/tree/main/gcpc2018/jigsawpuzzle

Fixing it

• I'm willing to implement the fix myself

[ghamerly]

Problem is now installed (as jigsawpuzzle2) and added to Open and Edu problem pools.