Proposal: include leap-seconds.list from tzdata

[Mallory Adams <malloryadams%fastmail.com@localhost>]

Hi,

I'd like to propose including one more file from the tzdata 
distribution: `leap-seconds.list`.

The reason I'm asking is because I'm in the process of porting Hare ( 
https://harelang.org/ ) to NetBSD and Hare's `time` module requires this 
file. I know I can fetch the file while building the package in pkgsrc, 
but I figured I can make this small ask and maybe make packaging a 
little easier for myself.

This file has some overlap with the contents of 
`/usr/share/zoneinfo/leapseconds`, but the leap seconds in 
`leap-seconds.list` are available as NTP timestamps instead of 
year/month/date/hours/minutes/seconds.

If compatibility is a concern, here's where some other OSes store the file:

OpenBSD: /usr/share/zoneinfo/leap-seconds.list
Debian:  /usr/share/zoneinfo/leap-seconds.list
FreeBSD: /var/db/ntpd.leap-seconds.list

Thanks,
Mallory