add new option over_write_on_duplicate

Author: mortza

src/LfmPath.php

@@ -248,7 +248,7 @@ private function uploadValidator($file)
 
         $new_file_name = $this->getNewName($file);
 
-        if ($this->setName($new_file_name)->exists()) {
+        if ($this->setName($new_file_name)->exists() && !config('lfm.over_write_on_duplicate')) {
             return $this->error('file-exist');
         }
 

src/config/lfm.php

@@ -25,6 +25,11 @@
     // Use relative paths (without domain)
     'relative_paths' => false,
 
+    // behavior on files with identical name
+    // setting it to true cause old file replace with new one
+    // setting it to false show `error-file-exist` error and stop upload
+    'over_write_on_duplicate' => false,
+
     /*
     |--------------------------------------------------------------------------
     | Multi-User Mode