onProgress percentage type wrong

[vincerubinetti]

The type definition says percentage is a string, but it can also be NaN, so the type should be string | number.

On a related note, I find it weird that percent is a toFixed-stringified version of the number rather than just a number. This would make the type more consistently and expectedly just number. Also I find it a little unexpected that the range of it is 0 to 100 instead of 0 to 1, but that's more of a preference.

If you ever making a breaking change to this library, these changes would be welcome.

[ibrod83]

You're right, that was some stupid misunderstanding on my part. As you said, this is breaking change, so perhaps in the future