Add page turn on power button press (#286)

## Summary

* **What is the goal of this PR?** 
* This PR adds a setting to (additionally) map the forward page turn
onto the powerbutton when in `EPUBReaderActivity` and powerbutton short
press is not mapped to sleep mode. I find the powerbutton to be exactly
where my thumb is while reading so it is very convenient to map the
forwardpage turn to that. Maybe Im not alone with this ^^
* **What changes are included?**

## Additional Context

* Add any other information that might be helpful for the reviewer
(e.g., performance implications, potential risks, specific areas to
focus on).

src/CrossPointSettings.h

@@ -52,6 +52,9 @@ class CrossPointSettings {
   // E-ink refresh frequency (pages between full refreshes)
   enum REFRESH_FREQUENCY { REFRESH_1 = 0, REFRESH_5 = 1, REFRESH_10 = 2, REFRESH_15 = 3, REFRESH_30 = 4 };
 
+  // Short power button press actions
+  enum SHORT_PWRBTN { IGNORE = 0, SLEEP = 1, PAGE_TURN = 2 };
+
   // Sleep screen settings
   uint8_t sleepScreen = DARK;
   // Sleep screen cover mode settings
@@ -61,8 +64,8 @@ class CrossPointSettings {
   // Text rendering settings
   uint8_t extraParagraphSpacing = 1;
   uint8_t textAntiAliasing = 1;
-  // Duration of the power button press
+  // Short power button click behaviour
-  uint8_t shortPwrBtn = 0;
+  uint8_t shortPwrBtn = IGNORE;
   // EPUB reading orientation settings
   // 0 = portrait (default), 1 = landscape clockwise, 2 = inverted, 3 = landscape counter-clockwise
   uint8_t orientation = PORTRAIT;
@@ -88,7 +91,9 @@ class CrossPointSettings {
   // Get singleton instance
   static CrossPointSettings& getInstance() { return instance; }
 
-  uint16_t getPowerButtonDuration() const { return shortPwrBtn ? 10 : 400; }
+  uint16_t getPowerButtonDuration() const {
+    return (shortPwrBtn == CrossPointSettings::SHORT_PWRBTN::SLEEP) ? 10 : 400;
+  }
   int getReaderFontId() const;
 
   bool saveToFile() const;

src/activities/reader/EpubReaderActivity.cpp

@@ -152,6 +152,8 @@ void EpubReaderActivity::loop() {
   const bool prevReleased = mappedInput.wasReleased(MappedInputManager::Button::PageBack) ||
                             mappedInput.wasReleased(MappedInputManager::Button::Left);
   const bool nextReleased = mappedInput.wasReleased(MappedInputManager::Button::PageForward) ||
+                            (SETTINGS.shortPwrBtn == CrossPointSettings::SHORT_PWRBTN::PAGE_TURN &&
+                             mappedInput.wasReleased(MappedInputManager::Button::Power)) ||
                             mappedInput.wasReleased(MappedInputManager::Button::Right);
 
   if (!prevReleased && !nextReleased) {

src/activities/reader/XtcReaderActivity.cpp

@@ -112,6 +112,8 @@ void XtcReaderActivity::loop() {
   const bool prevReleased = mappedInput.wasReleased(MappedInputManager::Button::PageBack) ||
                             mappedInput.wasReleased(MappedInputManager::Button::Left);
   const bool nextReleased = mappedInput.wasReleased(MappedInputManager::Button::PageForward) ||
+                            (SETTINGS.shortPwrBtn == CrossPointSettings::SHORT_PWRBTN::PAGE_TURN &&
+                             mappedInput.wasReleased(MappedInputManager::Button::Power)) ||
                             mappedInput.wasReleased(MappedInputManager::Button::Right);
 
   if (!prevReleased && !nextReleased) {

src/activities/settings/SettingsActivity.cpp

@@ -21,7 +21,7 @@ const SettingInfo settingsList[settingsCount] = {
     SettingInfo::Enum("Status Bar", &CrossPointSettings::statusBar, {"None", "No Progress", "Full"}),
     SettingInfo::Toggle("Extra Paragraph Spacing", &CrossPointSettings::extraParagraphSpacing),
     SettingInfo::Toggle("Text Anti-Aliasing", &CrossPointSettings::textAntiAliasing),
-    SettingInfo::Toggle("Short Power Button Click", &CrossPointSettings::shortPwrBtn),
+    SettingInfo::Enum("Short Power Button Click", &CrossPointSettings::shortPwrBtn, {"Ignore", "Sleep", "Page Turn"}),
     SettingInfo::Enum("Reading Orientation", &CrossPointSettings::orientation,
                       {"Portrait", "Landscape CW", "Inverted", "Landscape CCW"}),
     SettingInfo::Enum("Front Button Layout", &CrossPointSettings::frontButtonLayout,