Support for months when serializing `Duration` to ISO8601 string

[ThorodanBrom]

Hello,

Is it possible to get support for months is not present in the Duration to ISO8601 string here. The same scaling logic of 30 days in a month when converting the string to Duration could be used.

speedate/src/duration.rs

Lines 61 to 101 in 6fafc2c

	impl fmt::Display for Duration {
	fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
	if !self.positive {
	write!(f, "-")?;
	}
	write!(f, "P")?;
	if self.day != 0 {
	let year = self.day / 365;
	if year != 0 {
	write!(f, "{year}Y")?;
	}
	let day = self.day % 365;
	if day != 0 {
	write!(f, "{day}D")?;
	}
	}
	if self.second != 0 || self.microsecond != 0 {
	let (hour, minute, sec) = self.to_hms();
	write!(f, "T")?;
	if hour != 0 {
	write!(f, "{hour}H")?;
	}
	if minute != 0 {
	write!(f, "{minute}M")?;
	}
	if sec != 0 || self.microsecond != 0 {
	write!(f, "{sec}")?;
	if self.microsecond != 0 {
	let mut s = arrayvec::ArrayString::<6>::new();
	write!(s, "{:06}", self.microsecond)?;
	write!(f, ".{}", s.trim_end_matches('0'))?;
	}
	write!(f, "S")?;
	}
	}
	if self.second == 0 && self.microsecond == 0 && self.day == 0 {
	write!(f, "T0S")?;
	}
	Ok(())
	}
	}

Or is there a specific reason that this was never implemented?

Thanks