8: Add rolls to items on actor sheets

- Utilized the revisions made to roll syntax to allow for rollable
  buttons on item lists on actor sheets. Rolls are evaluated using
  `@items.ITEM.KEY`, where ITEM is the item name (slugified), and KEY is
  an attribute key for a formula attribute.

module/simple.js

@@ -82,4 +82,11 @@ Hooks.once("init", async function() {
     }
   }
 
+  /**
+   * Slugify a string.
+   */
+  Handlebars.registerHelper('slugify', function(value) {
+    return value.slugify({strict: true});
+  });
+
 });