Use more specific icons: icons for files

[HaudinFlorence]

For files that dont have an extension, the folder icon is used. Use a file icon instead so that the user understands that they must download that file to view it rather than clicking it expecting the folder to open up.

[DenisaCG]

Thanks for opening this issue!

Testing it on the latest version, it has been fixed. Once a file with an unknown extension is added, it retains its file icon.