Add immediate response for usb cable plug in / removal

lib/hal/HalGPIO.h

@@ -23,6 +23,9 @@ class HalGPIO {
   InputManager inputMgr;
 #endif
 
+  bool lastUsbConnected = false;
+  bool usbStateChanged = false;
+
  public:
   HalGPIO() = default;
 
@@ -41,6 +44,9 @@ class HalGPIO {
   // Check if USB is connected
   bool isUsbConnected() const;
 
+  // Returns true once per edge (plug or unplug) since the last update()
+  bool wasUsbStateChanged() const;
+
   enum class WakeupReason { PowerButton, AfterFlash, AfterUSBPower, Other };
 
   WakeupReason getWakeupReason() const;