[workflow] fixed example check workflow

[FrankLeeeee]

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Fixed #2553

📝 What does this PR do?

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This PR does 2 things:

1. fixed the matrix strategy such that other jobs will not stopped if any job fails
2. separate the workflow to three yaml files corresponding to different event trigger for better readability and maintenability
3. updated readme to categorize the workflows based on functionality

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[github-actions]

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