add sortFragmentsOnSync option, makes it possible to avoid unwanted sorting in editing environments like slides.com

js/config.js

@@ -287,6 +287,10 @@ export default {
 	// Time before the cursor is hidden (in ms)
 	hideCursorTime: 5000,
 
+	// Should we automatmically sort and set indices for fragments
+	// at each sync? (See Reveal.sync)
+	sortFragmentsOnSync: true,
+
 	// Script dependencies to load
 	dependencies: [],
 

js/reveal.js

@@ -1471,7 +1471,9 @@ export default function( revealElement, options ) {
 		// Write the current hash to the URL
 		location.writeURL();
 
-		fragments.sortAll();
+		if( config.sortFragmentsOnSync === true ) {
+			fragments.sortAll();
+		}
 
 		controls.update();
 		progress.update();