Add support for debouncing non-GPIO inputs.

include/PicoDebounceButton/PicoDebounceButton.hpp

@@ -36,11 +36,34 @@ class PicoDebounceButton
     gpio_pull_up(mPin);
   }
 
+  // The constructor can be used without a pin number;
+  // if so, you will need to manually pass a value to update()
+  // The default interval is 10ms.
+  // The default state is PRESSED.
+  // The default invert is false.
+  explicit PicoDebounceButton(uint16_t interval = 10,
+                              bool state = PRESSED,
+                              bool invert = false)
+      : mInterval(interval)
+      , mState(state)
+      , mInvert(invert)
+  {
+  }
+
   // The update() method should be called in the loop() function. It updates the
   // button state and returns true if the button state has changed.
-  auto update()
+  bool update()
+  {
+    return update(gpio_get(mPin));
+  }
+
+  // The update() method should be called in the loop() function.
+  // If no pin is specified, you need to pass the latest state value into
+  // update() as a parameter.
+  // It updates the button state and returns true if the button state has changed.
+  bool update(uint8_t val)
   {
-    bool currentState = mInvert ? !gpio_get(mPin) : gpio_get(mPin);
+    bool currentState = mInvert ? !val : val;
     uint32_t now = to_ms_since_boot(get_absolute_time());
     if (currentState != mLastState) {
       mLastStateTime = now;