Add initial Copilot instructions #3926

Job	Run time
Resolve environment (macos-latest, linked)	1m 55s
Resolve environment (windows-latest, default)	2m 14s
Resolve environment (macos-latest, default)	1m 59s
Resolve environment (windows-latest, linked)	2m 16s
Resolve environment (ubuntu-latest, default)	36s
Resolve environment (macos-latest, nightly-latest)	1m 58s
Resolve environment (ubuntu-latest, linked)	33s
Resolve environment (windows-latest, nightly-latest)	2m 34s
Resolve environment (ubuntu-latest, nightly-latest)	36s
	14m 41s

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