Calculator: The equal key will now also finish the operation

Prior to this if you typed "1+2=" you would not get the answer, instead
you'd be left with "2" on the screen; Calculator wanted you to hit the
enter key to get the answer. Now you can either use the enter or the
equal key to finish the operation and get the answer.

Userland/Applications/Calculator/CalculatorWidget.cpp

@@ -152,7 +152,7 @@ void CalculatorWidget::keydown_event(GUI::KeyEvent& event)
     m_equals_button->set_focus(true);
     m_equals_button->set_focus(false);
 
-    if (event.key() == KeyCode::Key_Return) {
+    if (event.key() == KeyCode::Key_Return || event.key() == KeyCode::Key_Equal) {
         m_keypad.set_value(m_calculator.finish_operation(m_keypad.value()));
     } else if (event.code_point() >= '0' && event.code_point() <= '9') {
         m_keypad.type_digit(event.code_point() - '0');