Document how to add appendix slides after the bibliography

pandoc/citeproc generates the reference list at the end of the document
body, so a chapter following the references would swallow it. Document
the ::: {#refs} placement div in the README (Rmd source and rendered
README.md in sync).

Change-Id: I7b701f4fc33178ce9aedb00c52a275d48b66e6c1
diff --git a/README.Rmd b/README.Rmd
index 40d2e63..436b961 100644
--- a/README.Rmd
+++ b/README.Rmd
@@ -428,6 +428,35 @@
 
 No other plugins can be added in `revealjs_presentation()`. You can open feature request for new plugins or you would need to use a custom template to write your own HTML format including custom plugins.
 
+## Bibliography and Appendix Slides
+
+When you cite with `[@key]` and set a `bibliography:` in the yaml header, pandoc/citeproc generates the reference list **at the very end of the document body**. That is fine when the references are your last content:
+
+```markdown
+# References
+
+## References
+```
+
+If you want slides to follow the references -- typically an appendix with spare slides -- the bibliography would otherwise end up inside your last appendix slide. Place it explicitly with a `::: {#refs}` fenced div, and the appendix forms its own chapter group after the references; navigation and slide numbering keep working:
+
+```markdown
+# References
+
+## References
+
+::: {#refs}
+:::
+
+# Appendix
+
+## Spare slide
+
+- Some backup material
+```
+
+The `{#refs}` placeholder itself does not produce a slide.
+
 ## Advanced Customization
 
 ### Includes
diff --git a/README.md b/README.md
index 766d096..cf97b4d 100644
--- a/README.md
+++ b/README.md
@@ -514,6 +514,42 @@
 feature request for new plugins or you would need to use a custom
 template to write your own HTML format including custom plugins.
 
+## Bibliography and Appendix Slides
+
+When you cite with `[@key]` and set a `bibliography:` in the yaml
+header, pandoc/citeproc generates the reference list **at the very end
+of the document body**. That is fine when the references are your last
+content:
+
+``` markdown
+# References
+
+## References
+```
+
+If you want slides to follow the references – typically an appendix
+with spare slides – the bibliography would otherwise end up inside your
+last appendix slide. Place it explicitly with a `::: {#refs}` fenced
+div, and the appendix forms its own chapter group after the references;
+navigation and slide numbering keep working:
+
+``` markdown
+# References
+
+## References
+
+::: {#refs}
+:::
+
+# Appendix
+
+## Spare slide
+
+- Some backup material
+```
+
+The `{#refs}` placeholder itself does not produce a slide.
+
 ## Advanced Customization
 
 ### Includes