Fix safari+firefox with service worker: clone file.encodedName on yield

[zakstucke]

Love the library. I encountered a very weird issue i painstakingly debugged, resulting in this PR.

Setup:

• Using https://github.com/jimmywarting/native-file-system-adapter
• Safari/firefox (meaning the service worker fallback will be used, chrome has no issue)
• Giving client zip an async iterator of ArrayBuffer chunks, rather than a blob or file (not sure if relevant, but could be)

Error occurs on closing the zip (i.e. once all files have been included and the stream is being closed by client-zip)
Firefox error:
MessagePort.postMessage: attempting to access detached ArrayBuffer

Safari error:
Unhandled Promise Rejection: DataCloneError: The object can not be cloned.

The firefox error is the actual cause, the safari one gets hidden behind the above opaque one.

What I think is happening and why this PR fixes it:

• When service worker is being used, the buffers get transferred to the service worker.
• Not sure on exactly how the zipping works, but it looks like file.encodedName ends up getting sent twice during the zipping process, probably with the file, and in the zip's manifest
• With service worker, means needs to be transferred twice, therefore this error occurs as the buffers already been transferred.
• So by cloning the buffer on the first send, the same buffer will no longer be transferred twice, and no issue!

This change works for me now on both safari and firefox.

Thanks!

[Touffy]

Your analysis is correct. The file name buffer is used twice in the stream — in the file header and the central repository (the "index" of the archive) — and of course it can't be transferred twice (which is happening because you're running client-zip in the client window, and the Native File System adapter is transferring the stream to the Service Worker).

[zakstucke]

Great. Thanks!

[Touffy]

I'll publish this evening.