Fix type to match implementation

[yinm]

In implementation, CopyStatus has a writtenBytes property instead of a written property.

e.g.

cpy/index.js

Lines 217 to 220 in 7d6e8be

	const fileStatus = copyStatus.get(event.sourcePath) || {
	writtenBytes: 0,
	percent: 0,
	};

So, I fixed type to match implementation.