Add Slide Mode

using reveal.js
and some part of reveal-md

public/plugin/markdown/example.md

@@ -0,0 +1,31 @@
+# Markdown Demo
+
+
+
+## External 1.1
+
+Content 1.1
+
+Note: This will only appear in the speaker notes window.
+
+
+## External 1.2
+
+Content 1.2
+
+
+
+## External 2
+
+Content 2.1
+
+
+
+## External 3.1
+
+Content 3.1
+
+
+## External 3.2
+
+Content 3.2