feat: add power button short press for quick access to footnotes (#1658)

src/CrossPointSettings.h

@@ -134,7 +134,7 @@ class CrossPointSettings {
   };
 
   // Short power button press actions
-  enum SHORT_PWRBTN { IGNORE = 0, SLEEP = 1, PAGE_TURN = 2, FORCE_REFRESH = 3, SHORT_PWRBTN_COUNT };
+  enum SHORT_PWRBTN { IGNORE = 0, SLEEP = 1, PAGE_TURN = 2, FORCE_REFRESH = 3, FOOTNOTES = 4, SHORT_PWRBTN_COUNT };
 
   // Hide battery percentage
   enum HIDE_BATTERY_PERCENTAGE { HIDE_NEVER = 0, HIDE_READER = 1, HIDE_ALWAYS = 2, HIDE_BATTERY_PERCENTAGE_COUNT };
@@ -230,6 +230,8 @@ class CrossPointSettings {
   uint8_t uiTheme = LYRA;
   // Sunlight fading compensation
   uint8_t fadingFix = 0;
+  // Power button return from footnotes (1 = enabled, 0 = disabled)
+  uint8_t pwrBtnFootnoteBack = 1;
   // Use book's embedded CSS styles for EPUB rendering (1 = enabled, 0 = disabled)
   uint8_t embeddedStyle = 1;
   // Focus Reading - emphasizes the first part of words with bold