Allow selecting next exercise with enter key

src/list.rs

@@ -83,7 +83,7 @@ fn handle_list(app_state: &mut AppState, stdout: &mut StdoutLock) -> Result<()>
                         }
                     }
                     KeyCode::Char('r') => list_state.reset_selected()?,
-                    KeyCode::Char('c') => {
+                    KeyCode::Char('c') | KeyCode::Enter => {
                         if list_state.selected_to_current_exercise()? {
                             return Ok(());
                         }