Attaches a file to element located by label, name, CSS or XPath
Path to file is relative current codecept directory (where codecept.json or codecept.conf.js is located).
File will be uploaded to remote system (if tests are running remotely).

```js
I.attachFile('Avatar', 'data/avatar.jpg');
I.attachFile('form input[name=avatar]', 'data/avatar.jpg');
```

@param {CodeceptJS.LocatorOrString} locator field located by label|name|CSS|XPath|strict locator.
@param {string} pathToFile local file path relative to codecept.json config file.