add a few more examples

inst/rmarkdown/templates/html_vignette/skeleton/skeleton.Rmd

@@ -35,3 +35,24 @@ The figure sizes have been customised so that you can easily put two images side
 plot(1:10)
 plot(10:1)
 ```
+
+You can enable figure captions by `fig_caption: yes` in YAML:
+
+    output:
+      rmarkdown::html_vignette:
+        fig_caption: yes
+
+Then you can use the chunk option `fig.cap = "Your figure caption."` in **knitr**.
+
+## More Examples
+
+You can write math expressions, e.g. $Y = X\beta + \epsilon$, footnotes^[A footnote here.], and tables, e.g. using `knitr::kable()`.
+
+```{r, echo=FALSE, results='asis'}
+knitr::kable(head(mtcars, 10))
+```
+
+Also a quote using `>`:
+
+> "He who gives up [code] safety for [code] speed deserves neither."
+([via](https://twitter.com/hadleywickham/status/504368538874703872))