[wip] implement command usecases

src/background/repositories/bookmark.js

@@ -0,0 +1,13 @@
+export default class BookmarkRepository {
+  async create(title, url) {
+    let item = await browser.bookmarks.create({
+      type: 'bookmark',
+      title,
+      url,
+    });
+    if (!item) {
+      throw new Error('Could not create a bookmark');
+    }
+    return item;
+  }
+}