bug#46742: Also support Asian government calendars in real live use by millions

[積丹尼 Dan Jacobson]

(info "(emacs) Calendar Systems") says
> 31.9.1 Supported Calendar Systems
> ---------------------------------
> The ISO commercial calendar is often used in business.
...
> projected to occur on March 20, 2025.  It is currently not clear what
> the official calendar of Iran will be at that time.
...
>    The Chinese calendar is a complicated system of lunar...

The article needs to make a sharp distinction between current official
calendars for each country vs. heirloom calendars for each culture.

https://en.wikipedia.org/wiki/Republic_of_China_calendar
https://en.wikipedia.org/wiki/North_Korean_calendar
https://en.wikipedia.org/wiki/Japanese_era_name
are calendars which are used on government documents and
thus are used by hundreds of millions of people every day.

(Half my mailbox is filled with government mails using it exclusively
$ perl -wlne 'print for /110/g' some_mail_from.*.gov.tw_body | wc -l
6
(except of course in the Date: header. Fortunately 2021.)

(Yes I wish they would go away, so I started a page
https://www.facebook.com/norocyear
but alas they are here to stay.)

Good thing is these calendars only differ in year from 2021. Months etc.
are not tampered with. (E.g., in Taiwan it is 110 this year.)

Therefore it would be easy for the Emacs calendar to implement them.

In any case they should be mentioned on the INFO page.