feat: add keyboard shortcuts for notes, the note list and the app

lib/markdown_view.dart

@@ -9,6 +9,7 @@ class MarkdownView extends StatefulWidget {
   final bool readOnly;
   final double fontSize;
   final FocusNode? focusNode;
+  final ScrollController? scrollController;
 
   const MarkdownView({
     super.key,
@@ -16,6 +17,7 @@ class MarkdownView extends StatefulWidget {
     this.readOnly = true,
     this.fontSize = 16,
     this.focusNode,
+    this.scrollController,
   });
 
   @override
@@ -40,6 +42,16 @@ class MarkdownViewState extends State<MarkdownView> {
     );
   }
 
+  /// Text offset at the top-left of the visible area.
+  int firstVisibleOffset() {
+    final box = _fieldKey.currentContext?.findRenderObject() as RenderBox?;
+    final editable = _findEditable(box);
+    if (box == null || editable == null) return 0;
+    return editable
+        .getPositionForPoint(box.localToGlobal(const Offset(1, 1)))
+        .offset;
+  }
+
   RenderEditable? _findEditable(RenderObject? node) {
     if (node is RenderEditable) return node;
     RenderEditable? found;
@@ -68,6 +80,7 @@ class MarkdownViewState extends State<MarkdownView> {
         key: _fieldKey,
         controller: widget.controller,
         focusNode: widget.focusNode,
+        scrollController: widget.scrollController,
         readOnly: widget.readOnly,
         showCursor: !widget.readOnly,
         expands: true,