Describe page range splitting for citation references (#2304)

From Quarto 1.11, the CSL `page` value is split into a first and last
page for each `citation_reference` tag, as well as for the document
citation. The split accepts a hyphen, en dash or em dash. A page list
such as `1-3, 7-9` gives only a first page.

Explicit `page-first` and `page-last` values take precedence over the
split. The Citation Fields table now documents this.

Related to quarto-dev/quarto-cli#15118

Author: cderv

docs/authoring/create-citeable-articles.qmd

@@ -247,7 +247,7 @@ Quarto's approach to emitting scholarly metadata is to take the standard CSL fie
 - - `page`
 
     ::: small
-    Will be split on `-` to create appropriate page metadata.
+    From Quarto 1.11, split on a hyphen, en dash or em dash into first and last page, for the document citation and for each `citation_reference`. A single page (`42`) or a list of pages (`1-3, 7-9`) gives only `citation_firstpage`. `page-first` and `page-last` take precedence when provided.
     :::
   - `citation_firstpage`