Extract default view keybindings and widget

Move generic view rendering and keybinding logic into a new default
module and
replace inline implementations with calls to the new helpers.

src/app/widgets/default.rs

@@ -0,0 +1,25 @@
+use crate::app::{App, widgets::KeybindingsWidget};
+use ratatui::{
+    buffer::Buffer,
+    layout::{Alignment, Constraint, Layout, Rect},
+    style::Stylize,
+    widgets::{Block, Borders, Paragraph, Widget},
+};
+
+pub fn default_view_widget(app: &App, area: Rect, buf: &mut Buffer) {
+    let vertical_layout: Layout = Layout::vertical([Constraint::Fill(1), Constraint::Length(4)]);
+
+    let [main_area, keybindings_area] = vertical_layout.areas(area);
+
+    Paragraph::new("Work in progress")
+        .alignment(Alignment::Center)
+        .yellow()
+        .block(
+            Block::new()
+                .gray()
+                .borders(Borders::LEFT | Borders::TOP | Borders::RIGHT),
+        )
+        .render(main_area, buf);
+
+    KeybindingsWidget::new(app.view).render(keybindings_area, buf);
+}

src/app/widgets/mod.rs

@@ -1,5 +1,7 @@
+pub mod default;
 pub mod keybindings;
 pub mod main_menu;
 
+pub use default::default_view_widget;
 pub use keybindings::KeybindingsWidget;
 pub use main_menu::main_menu_widget;