Document how to set GPSHPositioningError

[daniel]

I'm trying to set GPSHPositioningError, but I'm not sure how to do it.

I've tried this:

const accuracy = 123.45 // in meter
gpsIfd[piexif.GPSIFD.GPSHPositioningError] = [Math.round(accuracy), 1]

It works on iOS, but on Android GPSHPositioningError is shown as 0m when I inspect it in an exif viewer app.