add shrink_story to remove empty (including \s chars) sections

coretool.js

@@ -338,4 +338,14 @@ module.exports = {
     else // undefined, NaN, Infinity, {}
       return 0
   },
+
+  shrink_story (story) {
+    if (Array.isArray(story)) {
+      story = story.filter(section => Object.values(section).some(val => val?.trim?.())) // (section.text || section.image || section.video)?.trim?.()
+      return story
+    } else {
+      story = []
+      return story
+    }
+  }
 }