Add text input handling to settings popup

Introduce a `selected_setting_new_value` field in `SettingsState` and
initialize it.
Add `Backspace` and `WildCard(char)` actions with an `Input` group, and
corresponding keybindings.
Update `event_to_action` to map wildcard characters to
`Action::WildCard`.
Handle backspace and character input in `settings_keybindings` to edit
the new field.
Display the edited value in the settings popup and include the new
actions in the UI.

src/app/keybindings/settings.rs

@@ -7,6 +7,8 @@ use ratatui::crossterm::event::KeyEvent;
 pub fn settings_keybindings(app: &mut App, key_event: &KeyEvent) {
     if let Some(action) = event_to_action(&key_event) {
         match action {
+            // Action::Up,
+            // Action::Down,
             Action::Quit => app.exit = true,
             Action::Quit2 => app.exit = true,
             Action::Esc => app.view = View::MainMenu,
@@ -14,6 +16,22 @@ pub fn settings_keybindings(app: &mut App, key_event: &KeyEvent) {
                 app.game_states.settings_state.show_popup =
                     !app.game_states.settings_state.show_popup
             }
+            Action::Backspace => {
+                if app.game_states.settings_state.show_popup {
+                    app.game_states
+                        .settings_state
+                        .selected_setting_new_value
+                        .pop();
+                }
+            }
+            Action::WildCard(c) => {
+                if app.game_states.settings_state.show_popup {
+                    app.game_states
+                        .settings_state
+                        .selected_setting_new_value
+                        .push(c);
+                }
+            }
             _ => (),
         }
     }