Add fixers for backward compatibility

Author: pstasicki

src/Unwanted.php

@@ -24,14 +24,17 @@ public static function isUnwanted(string $name): bool
                 'not_operator_with_space',
                 'not_operator_with_successor_space',
                 'octal_notation',
+                'php_unit_attributes',
                 'php_unit_internal_class',
                 'php_unit_size_class',
                 'php_unit_strict',
                 'php_unit_test_class_requires_covers',
                 'phpdoc_summary',
                 'phpdoc_to_property_type',
+                'phpdoc_to_return_type',
                 'single_line_comment_spacing',
                 'single_line_throw',
+                'string_implicit_backslashes',
                 'strict_param',
                 'void_return',
                 'PhpCsFixerCustomFixers/constructor_empty_braces',