Mention use of copilot to diagnose and fix CI failures

In https://github.com/epiverse-trace/.github/pull/44/ @adamkucharski improved the contributing guide to lower the barrier of entry for new contributors who are not familiar with CI failures. We can further improve this by suggesting the use of GitHub copilot which is embedded in GitHub and offers help with interpreting and fixing CI failures. Here is [an example of it in action with EpiNow2](https://github.com/copilot/c/642ee06d-9b71-4f5f-b2b6-ee0611c8d44f).