FileExtractor's getType() should return string or array

[klinec]

I created my own YamlFileExtractor and the issue I had was that similar to php also yaml files can have different extentions .yaml or .yml. But method getType in https://github.com/php-translation/extractor/blob/master/src/FileExtractor/FileExtractor.php can return only string which is then compared to file extension. So I had to create another YmlFileExtractor.

I suggest to change the FileExtractor interface to

    /**
     * The file type the extractor supports.
     *
     * @return string|array
     */
    public function getType();

[ostrolucky]

Yes, need for array is obvious because of need to have block of code like such

extractor/src/Extractor.php

Lines 69 to 79 in 810f91c

	switch ($ext) {
	case 'php':
	case 'php5':
	case 'phtml':
	return 'php';
	case 'twig':
	return 'twig';
	case 'blade.php':
	return 'blade';
	default:
	return $ext;

[Nyholm]

I think you are correct. That is a BC break though... I'll make a PR.