Bytes will implicitly cast to StringView, but not to ReadonlyBytes. That
means that if you call
`Audio::Loader::create_plugin(mapped_file->bytes())`
it will silently use the `create_plugin(StringView path)` overload.
Reading audio data does not require that data to be writable, so let's
use ReadonlyBytes for it and avoid the footgun.
0a9fa85e86