Add reveal.js scroll view option to HTML writer (#11305)

* Add revealjs `scroll` view option to HTML writer
* Add `scrollSnap` option into default.revealjs

Closes #10052

Author: abdivasiyev

data/templates/default.revealjs

@@ -232,6 +232,19 @@ $endif$
         // devices. It is advisable to set this to a lower number than
         // viewDistance in order to save resources.
         mobileViewDistance: $mobileViewDistance$,
+$if(view)$
+
+        // Enable scroll view
+        view: '$view/nowrap$',
+        // see https://revealjs.com/scroll-view/#scrollbar
+        scrollProgress: $scrollProgress$,
+        // see https://revealjs.com/scroll-view/#url-activation
+        scrollActivationWidth: '$scrollActivationWidth$',
+        // see https://revealjs.com/scroll-view/#scroll-snapping
+        scrollSnap: '$scrollSnap$',
+        // Experimental. see https://revealjs.com/scroll-view/#scroll-snapping
+        scrollLayout: '$scrollLayout$',
+$endif$
 $if(parallaxBackgroundImage)$
 
         // Parallax background image

src/Text/Pandoc/Writers/HTML.hs

@@ -432,7 +432,11 @@ pandocToHtml opts (Pandoc meta blocks) = do
                          defField "transitionSpeed" ("default" :: Doc Text) .
                          defField "backgroundTransition" ("fade" :: Doc Text) .
                          defField "viewDistance" ("3" :: Doc Text) .
-                         defField "mobileViewDistance" ("2" :: Doc Text)
+                         defField "mobileViewDistance" ("2" :: Doc Text) .
+                         defField "scrollProgress" True .
+                         defField "scrollActivationWidth" ("0" :: Doc Text) .
+                         defField "scrollSnap" ("mandatory" :: Doc Text) .
+                         defField "scrollLayout" ("full" :: Doc Text)
                       else id) .
                   defField "document-css" (isNothing mCss && slideVariant == NoSlides) .
                   defField "quotes" (stQuotes st) .