COPT for MiniZinc Challenge

[Mako]

COPT is a MILP solver that is competitive with Gurobi according to the benchmarks linked below. It may be beneficial to include COPT in future MiniZinc Challenges.

Benchmarks: https://plato.asu.edu/bench.html
COPT software: https://github.com/COPT-Public/COPT-Release
COPT license: https://www.shanshu.ai/copt/
COPT user guide: https://guide.coap.online/copt/en-doc/index.html