Fix Copilot instructions to run mandatory steps

[RyanCavanaugh]

Acknowledgement

• I acknowledge that issues using this template may be closed without further explanation at the maintainer's discretion.

Comment

Copilot keeps forgetting to do very important mandatory steps before submitting its fixes:

• Doesn't run hereby lint, always start here!
• Doesn't run hereby runtests-parallel, this is a must!! It takes up to 15 minutes each time but it's so important to get this right. Patience is a virtue.
• Doesn't run hereby format as a last step. Our line endings may not be LF but we still like them to be consistent.

This is hurting the maintainers' feelings. Fix the copilot-instructions.md file so that it won't make this mistake again.

[MartinJohns]

Poor maintainers. 😢