Add contribution guidelines for pull requests to copilot review #4199

Job	Run time
Prepare CodeQL unit test matrix	9s
Run unit tests (cpp, 2.21.4, codeql-cli/v2.21.4, codeql-bundle-v2.21.4, ubuntu-latest-xl, codeql-...	1h 51m 35s
Run unit tests (c, 2.21.4, codeql-cli/v2.21.4, codeql-bundle-v2.21.4, ubuntu-latest-xl, codeql-cl...	39m 52s
Validate test results	5s
	2h 31m 41s

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