refactor: Improve error message for invalid YAML syntax

[ioncakephper]

Is your feature request related to a problem?

Currently, if a user tries to validate a file that contains invalid YAML syntax, the application may crash or
produce a complex error message from the js-yaml library. We should handle this gracefully and provide a clear,
user-friendly error message.

Describe the solution you'd like

Tasks:

1. In src/validate.js, locate the yaml.load() call within the validateYaml function.
2. Wrap this call in a try...catch block.
3. In the catch block, check if the error is a YAML parsing error.
4. If it is, return an object in the same format as a validation failure, but with a custom error message,
   e.g., { valid: false, errors: [{ message: 'The provided file is not a valid YAML document. Please check its
   syntax.' }] }.
5. Update the tests in test/validate.test.js to include a new test case that asserts this user-friendly error
   is returned when trying to validate a syntactically incorrect YAML file.

Describe alternatives you've considered

No response

Additional Context

No response