feat: add github output value

[acouvreur]

This feature allow users to output the validations errors as github error message using --output github.

This is very useful when this library is used as part of a validation tool in GitHub workflows.

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This is a very naive, non-optimized way of setting the error on the file at the line that errored.

printGitHub uses the following behavior:

1. Recursively prints the DetailedOutput
2. If an error exists
   1. Convert the InstanceLocation to a JSON Path
   2. Use the gjson library to retrieve the index of the JSON Path from the JSON file
   3. Use that index to retrieve the line number (split by line ending and then find in which line the index belongs by summing each line length)

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There's also no unit test, but it would need some for special cases, might work on that later.