Move core module to root

src/TOC.ts

@@ -0,0 +1,17 @@
+import Item from './Item';
+import ItemType from './ItemType';
+
+/**
+ * Table of contents usually parsed by  `DetectToc.ts`.
+ */
+export default class TOC {
+  constructor(public tocHeadlineItems: Item[], public pages: number[], public detectedHeadlineLevels: Set<ItemType>) {}
+
+  startPage(): number {
+    return Math.min(...this.pages);
+  }
+
+  endPage(): number {
+    return Math.max(...this.pages);
+  }
+}