[shellcheck] Add instructions for autofix when shell lint fails

### TL;DR

Did you know you can have shellcheck auto fix your linter errors?

`shellcheck -f diff FILENAME --enable=all | git apply` !!!

When that linter fails the output should mention that to people, because it will save them time.

### Detailed design

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### Alternatives considered

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### Additional information

_No response_

Find where the shell linter runs in the repository, likely in a GitHub Actions workflow or a script. Look for the command that invokes shellcheck and modify the output to include the autofix instruction. Test by running the linter locally to see the new message.

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