Reveal should be an outputFormat

Now any Hugo section can be configured to generate a presentation without altering its type, and the theme is more easily copied into existing sites without conflicting with any preexisting layouts.

exampleSite/content/home/body.md

@@ -22,7 +22,11 @@ weight = 20
 
 # reveal-hugo
 
-Create multiple presentations, one for each section in `content`.
+Create a presentation for any section by adding this to its `_index.md`:
+
+```toml
+outputs = ["Reveal"]
+```
 
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