* Add W3C Markup Validation Service Badge (#3833)
* Move helper functions into different file and added unit tests
* Remove unnecessary comments from spec file
* pr changes move code into transform method and validation of messages
* use joi.string().regex instead of custom validator
* Simplify the fetch, handle methods. Make Joi validation for string
* Remove empty parameter from tests and label from render method
* encodeUri on the doc and schema properties send to API
* Documentation and remove unnecessary Object.keys call
* Use regular expressions to make tests less brittle
* made service less for message and color more generic and less brittle
* Throw standard NoFound exception for invalid URL. Use w3c endpoint
* use sazerac for w3c-validation-helper.spec.js
* Replace documentation API url and API documentation url
* Switch back to https://validator.nu endpoint. Remove html4 assertions
* Increase strictness of NotFound checks
