function rangeToString(iRange) {
    if (iRange.offset < 0) {
        throw new RangeError(`Range.offset cannot be smaller than 0.`);
    }
    if (iRange.count && iRange.count <= 0) {
        throw new RangeError(`Range.count must be larger than 0. Leave it undefined if you want a range from offset to the end.`);
    }
    return iRange.count
        ? `bytes=${iRange.offset}-${iRange.offset + iRange.count - 1}`
        : `bytes=${iRange.offset}-`;
}
Generate a range string. For example:

"bytes=255-" or "bytes=0-511"

@param iRange -