Option to short-press power button. (#56)

Adresses #53 

Please check if we still need the code to "Give the user up to 1000ms to
start holding the power button, and must hold for
SETTINGS.getPowerButtonDuration()" - the power button should be pressed
already when waking up...

Also, decided to return before the delay to wait more to make the
behavior more immediate.

---------

Co-authored-by: Dave Allie <dave@daveallie.com>

src/CrossPointSettings.h

@@ -17,15 +17,18 @@ class CrossPointSettings {
 
   // Sleep screen settings
   uint8_t whiteSleepScreen = 0;
-
   // Text rendering settings
   uint8_t extraParagraphSpacing = 1;
+  // Duration of the power button press
+  uint8_t shortPwrBtn = 0;
 
   ~CrossPointSettings() = default;
 
   // Get singleton instance
   static CrossPointSettings& getInstance() { return instance; }
 
+  uint16_t getPowerButtonDuration() const { return shortPwrBtn ? 10 : 500; }
+
   bool saveToFile() const;
   bool loadFromFile();
 };