Safe Writer Laravel Package

#5 changes all exception classes to be non-instantiable and all theirs public method to be internal. Library exceptions can only be caught in the user code, cannot be thrown.

#5 changes all method declarations to have type hints and return types.

Adds function to safely writing files to avoid race conditions when the same file is written multiple times in a short time period, and errors on reading not fully written files. Example usage:

use Webimpress\SafeWriter\FileWriter;

$targetFile = __DIR__ . '/config-cache.php';
$content = "<?php\nreturn " . var_export($data, true) . ';';

FileWriter::writeFile($targetFile, $content, 0666);