Having folio number in page headers

[Omikhleia]

As in the middle example... (Screenshot from a Lulu.com article).

But

• When page nos are at the bottom of the page, they may (or not) be shown on a chapter or part initial page (I've seen both cases)
• When page nos are in the header, they are not shown obviously on a chapter or part initial page

It could be hard-coded to some extent, but to be checked how we can generalize the idea within our existing styling paradigm and layout concept ^^

[Omikhleia]

Shifting from target 2.1 to later - This clearly won't make it in due time (in the remaining time frame for 2.1)

[Omikhleia]

Shifting again - I need 2.2 by November and won't be able to consider this.

[Omikhleia]

Additional constraint: What about folios alternating between headers and footers as in @jodros 's example here: sile-typesetter/sile#1952 (comment)

(Technically it's folios in top or bottom margin areas, but it challenges the original idea from the description towards some more general solution...)