refactor: improve output messages

[jaredmcateer]

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Remove --check option to avoid this error is a little ambiguous (e.g., will it just suppress the error). Updated to let the user know what will happen if they remove it.

$ npx codeowners-generator generate --check
  
Custom configuration found in /Users/jared.mcateer/Projects/test/package.json
✖ We encountered an error: We found differences between the existing codeowners file and 
the generated rules. Remove --check option to fix this.

Added message for when --check is successful, rather than telling the user the file was created, which should not happen with that command.

$ npx codeowners-generator generate --check
  
Custom configuration found in /Users/jared.mcateer/Projects/test/package.json
CODEOWNERS file up to date! location: .github/CODEOWNERS

Changed message for when new generated rules change the CO file, rather than saying a file was created, let them know the generated rules have changed. A CO file being created should be incredibly rare (i.e., maybe the first time this tool is run in a project).

$ npx codeowners-generator generate

Custom configuration found in /Users/jared.mcateer/Projects/test/package.json
CODEOWNERS file updated with the generated rules! location: .github/CODEOWNERS