address #3 with option

README.md

@@ -43,6 +43,7 @@ format:
   - `Numbered`: Numbered reference style, usually used with `journal.cite-style: sn-vancouver`.
   - `referee`: double spaced for first submissions
   - `lineno`: print line numbers in the margin
+- `equal-margins`: set equal margins on even and odd pages
 
 Since `cite-method: citeproc` is the
 [default](https://quarto.org/docs/authoring/footnotes-and-citations.html#sec-biblatex),

_extensions/nature/partials/doc-class.tex

@@ -10,4 +10,8 @@
 $for(classoption)$
   $classoption$$sep$,
 $endfor$
-]{sn-jnl}
+]{sn-jnl}
+
+$if(equal-margins)$
+\setlength\evensidemargin{\oddsidemargin}
+$endif$

template.qmd

@@ -10,6 +10,7 @@ format:
     # to use the bst styles from the upstream template.
     cite-method: natbib
     keep-tex: true
+    equal-margins: false
 author:
   - name: Author One
     affiliations:
@@ -106,3 +107,7 @@ row 3    & data 7   & data 8  & data 9\footnotemark[2]  \\
 <!-- the pattern below controls the placement of the references -->
 :::{#refs}
 :::
+
+# Appendix {.appendix}
+
+{{< lipsum 5 >}}