Add footer for ids theme

Change-Id: If85c9fe027fb9cc45677068474b21d15d32e7134
diff --git a/R/revealjs_presentation.R b/R/revealjs_presentation.R
index 881364f..178a08c 100644
--- a/R/revealjs_presentation.R
+++ b/R/revealjs_presentation.R
@@ -191,6 +191,11 @@
   }
   args <- c(args, pandoc_variable_arg("theme", theme))
 
+  if (theme == "ids") {
+    args <- c(args, pandoc_variable_arg("theme-ids"))
+    fig_height = 7
+    fig_width = 12
+  }
 
   # transition
   transition <- match.arg(transition, revealjs_transitions())