update footnote doc; fix a bug in row_spec
diff --git a/man/footnote.Rd b/man/footnote.Rd
index b2cc29c..8cda4fc 100644
--- a/man/footnote.Rd
+++ b/man/footnote.Rd
@@ -49,3 +49,8 @@
 also possible to specify footnote section header one by one and print
 footnotes as a chunk of texts.
 }
+\examples{
+x <- mtcars[1:5, 1:5]
+footnote(knitr::kable(dt, "html"), alphabet = c("Note a", "Note b"))
+
+}