feat: output spell checking result

[Jason3S]

Output the results of the action:

outputs:
  success:
    description: |
      "true" if no spelling issues were found, otherwise "false".
  number_of_files_checked:
    description: |
      The actual number of files that were checked.
  number_of_issues:
    description: |
      The number of issues found.
  number_of_files_with_issues:
    description: |
      The number of files that had issues.
  files_with_issues:
    description: |
      List of files with issues. Use `fromJSON()` to decode.
      The files are relative to the repository root.
  results:
    description: |
      The JSON encoded results.

Example Output:

{
  "success": "false",
  "number_of_files_checked": "3",
  "number_of_issues": "2",
  "number_of_files_with_issues": "1",
  "files_with_issues": "[\"src/withErrors.ts\"]",
  "result": "{\"success\":false,\"number_of_issues\":2,\"number_of_files_checked\":3,\"files_with_issues\":[\"src/withErrors.ts\"]}"
}