Add initial Copilot instructions #9719

Job	Run time
check-codeql-versions	51s
analyze-actions	55s
analyze-javascript (ubuntu-24.04, linked)	3m 53s
analyze-javascript (ubuntu-22.04, linked)	3m 55s
analyze-javascript (ubuntu-22.04)	4m 5s
analyze-javascript (windows-2022)	6m 12s
analyze-javascript (ubuntu-24.04)	3m 46s
analyze-javascript (macos-14)	3m 53s
analyze-javascript (windows-2025, linked)	5m 14s
analyze-javascript (windows-2025)	5m 17s
analyze-javascript (macos-13)	5m 45s
analyze-javascript (macos-13, linked)	8m 0s
analyze-javascript (macos-15)	4m 39s
analyze-javascript (macos-14, linked)	5m 16s
analyze-javascript (windows-2022, linked)	6m 12s
analyze-javascript (macos-15, linked)	4m 35s
	1h 12m 28s

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