feat: add quotations from marked text, with citations and sharing

app/lib/presentation/reader/reader_screen.dart

@@ -336,6 +336,14 @@ class _ReaderScreenState extends State<ReaderScreen> {
         },
         onFormChange: (form, values) =>
             deps.browser.narrowWhileTyping(form.action, values),
+        // The reader's marked text is kept with the page it came from, so
+        // its citation can name the author when the page did.
+        onSaveQuotation: (text) => deps.db.addQuotation(
+              quote: text,
+              pageUrl: page.url,
+              pageTitle: page.title,
+              author: page.author,
+            ),
         fetchImageBytes: deps.browser.fetchImageBytes,
         scrollController: _scroll,
       );