class Webpacker::Manifest

When the user provides a name with a file extension, we want to try to strip it off.
manifest hash the entrypoints are defined by their pack name without the extension.
The `manifest_name` method strips of the file extension of the name, because in the

def manifest_name(name, pack_type)
  return name if File.extname(name.to_s).empty?
  File.basename(name, pack_type)
end