style: single quotes

#23

Signed-off-by: Daniel Kesselberg <mail@danielkesselberg.de>

src/Config.php

@@ -63,6 +63,7 @@ public function getRules() : array {
 			'single_class_element_per_statement' => true,
 			'single_import_per_statement' => true,
 			'single_line_after_imports' => true,
+			'single_quote' => ['strings_containing_single_quote_chars' => false],
 			'switch_case_space' => true,
 			'types_spaces' => ['space' => 'none', 'space_multiple_catch' => 'none'],
 			'visibility_required' => [