add css for csl in Pandoc's templates

NEWS.md

@@ -18,6 +18,8 @@
 
 - `serve_book()` will refresh correctly now when using subdirectories with `rmd_subdir` (thanks, @shenfei, #834).
 
+- Added the same CSS as in default Pandoc's template for when a CSL is used (#1045).   
+
 ## MINOR CHANGES
 
 - `anchor_sections = TRUE` becomes the default for `bookdown::gitbook()`.

inst/templates/default.html

@@ -86,6 +86,34 @@
 </style>
 $endif$
 
+$if(csl-css)$
+<style type="text/css">
+/* Used with Pandoc 2.11+ new --citeproc when CSL is used */
+div.csl-bib-body { }
+div.csl-entry {
+  clear: both;
+$if(csl-entry-spacing)$
+  margin-bottom: $csl-entry-spacing$;
+$endif$
+}
+.hanging div.csl-entry {
+  margin-left:2em;
+  text-indent:-2em;
+}
+div.csl-left-margin {
+  min-width:2em;
+  float:left;
+}
+div.csl-right-inline {
+  margin-left:2em;
+  padding-left:1em;
+}
+div.csl-indent {
+  margin-left: 2em;
+}
+</style>
+$endif$
+
 $for(css)$
 <link rel="stylesheet" href="$css$" $if(html5)$$else$type="text/css" $endif$/>
 $endfor$

inst/templates/gitbook.html

@@ -77,6 +77,34 @@
 </style>
 $endif$
 
+$if(csl-css)$
+<style type="text/css">
+/* Used with Pandoc 2.11+ new --citeproc when CSL is used */
+div.csl-bib-body { }
+div.csl-entry {
+  clear: both;
+$if(csl-entry-spacing)$
+  margin-bottom: $csl-entry-spacing$;
+$endif$
+}
+.hanging div.csl-entry {
+  margin-left:2em;
+  text-indent:-2em;
+}
+div.csl-left-margin {
+  min-width:2em;
+  float:left;
+}
+div.csl-right-inline {
+  margin-left:2em;
+  padding-left:1em;
+}
+div.csl-indent {
+  margin-left: 2em;
+}
+</style>
+$endif$
+
 $for(css)$
 <link rel="stylesheet" href="$css$" $if(html5)$$else$type="text/css" $endif$/>
 $endfor$