Clarify blog backlink requirements in CONTRIBUTING.md and ONBOARDING.… #15

Job	Run time
Lint Bash examples	34s
Lint Ruby examples	13s
Lint Python examples	9s
Lint Node.js examples	30s
Lint Kotlin examples	7m 37s
Validate content quality	6s
Validate example pack structure	6s
Lint C# examples	8m 30s
Lint Rust examples	42m 8s
Lint Go examples	44s
Lint PHP examples	22s
Lint Java examples	3m 42s
	1h 4m 41s

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