feat: enable editing from the down button in calc sample

samples/calc-02/index.js

@@ -356,7 +356,17 @@ constButton.addEventListener('click', (event) => {
 
 leftButton.addEventListener('click', () => {});
 
-downButton.addEventListener('click', () => {});
+downButton.addEventListener('click', () => {
+if (!calc.isEditing && calc.isValidIndex(0)) {
+	const value = calc.stack[0];
+	calc.remove(0);
+	calc.isEditing = true;
+	calc.inputValue = calc.formatNumber(value);
+	render();
+	focusInput();
+}
+});
+
 
 rightButton.addEventListener('click', () => {
 	execute('swap');