Normalize line endings in file content previews.

Author: krulis-martin

app/V1Module/presenters/UploadedFilesPresenter.php

@@ -264,6 +264,7 @@ public function actionContent(string $id, ?string $entry = null)
         // Remove UTF BOM prefix...
         $utf8bom = "\xef\xbb\xbf";
         $contents = Strings::replace($contents, "~^$utf8bom~");
+        $contents = str_replace($contents, "\r\n", "\n"); // normalize line endings
 
         $fixedContents = @mb_convert_encoding($contents, 'UTF-8', 'UTF-8');