Disable led display after 10 seconds to save energy

Going to sleep and waking on an interrupt generated by the button would
save even more energy, but it our current chip unfortunately has problems
waking up reliably.

code/code.ino

@@ -48,6 +48,7 @@ void setup() {
 }
 
 enum class State : uint8_t {
+    Sleep,
     Idle,
     Menu,
     Counting,
@@ -64,6 +65,12 @@ void loop() {
     auto event = button.event(debounce.event(buttonPressed));
 
     switch(state) {
+        case State::Sleep:
+            if(buttonPressed) {
+                digitalWrite(DISPLAY_ENABLE, 0);
+                state = State::Idle;
+                timeout = millis();
+            }
         case State::Idle:
             if(event == ButtonEvent::Press) {
                 state = State::Slowing;
@@ -72,6 +79,9 @@ void loop() {
                 timeout = millis();
             } else if(event == ButtonEvent::DoublePress) {
                 state = State::Menu;
+            } else if((uint16_t) millis() - timeout >= 10000) {
+                digitalWrite(DISPLAY_ENABLE, 1);
+                state = State::Sleep;
             }
             break;
         case State::Menu:
@@ -79,6 +89,7 @@ void loop() {
             display.setDash();
             display.write();
             state = State::Idle;
+            timeout = millis();
             break;
         case State::Counting:
             if(event == ButtonEvent::LongPress) {
@@ -95,6 +106,7 @@ void loop() {
         case State::Slowing:
             slowdown();
             state = State::Idle;
+            timeout = millis();
             break;
     }
 }