Note: Due to Chromium's bug it's not possible to correctly set Binary String (ByteString) as a header value in Service Worker. Use Firefox for this demo. [Readme on GH]
Filename: "123---ファイル---💧⚡🔥---xxx.txt"

Without quotes

The expected header (ByteString):
Click me to download 0


Quoted

The expected header (ByteString):
Click me to download 1


rfc5987

The expected header (ByteString):
Click me to download 2