validateLineBreak() function in CSV File does not check for Mac Line Breaks

[ssmusoke]

It is not clear why Mac line breaks are allowed at

https://github.com/keboola/php-csv/blob/eb77f51e22d3e13a8e14a5d5a0b588cf9e8c56c5/src/CsvFile.php#L183-186

yet they are not included in the validation at

php-csv/src/CsvFile.php

Line 408 in eb77f51

if (in_array($lineBreak, ["\r\n", "\n"])) {

[ssmusoke]

PR #30