add settings for reader screen margin (#223)

## Summary

* **What is the goal of this PR?** 
* This PR adds a setting to control the top left and right margins of
the reader screen in 4 sizes (5, 10, 20, 40 pt?) and defaults to `SMALL`
which is equivalent to the fixed margin of 5 that was already in use
before.
* **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).

---------

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

src/activities/settings/SettingsActivity.h

@@ -11,14 +11,37 @@
 
 class CrossPointSettings;
 
-enum class SettingType { TOGGLE, ENUM, ACTION };
+enum class SettingType { TOGGLE, ENUM, ACTION, VALUE };
 
 // Structure to hold setting information
 struct SettingInfo {
   const char* name;                        // Display name of the setting
   SettingType type;                        // Type of setting
-  uint8_t CrossPointSettings::* valuePtr;  // Pointer to member in CrossPointSettings (for TOGGLE/ENUM)
+  uint8_t CrossPointSettings::* valuePtr;  // Pointer to member in CrossPointSettings (for TOGGLE/ENUM/VALUE)
   std::vector<std::string> enumValues;
+
+  struct ValueRange {
+    uint8_t min;
+    uint8_t max;
+    uint8_t step;
+  };
+  // Bounds/step for VALUE type settings
+  ValueRange valueRange;
+
+  // Static constructors
+  static SettingInfo Toggle(const char* name, uint8_t CrossPointSettings::* ptr) {
+    return {name, SettingType::TOGGLE, ptr};
+  }
+
+  static SettingInfo Enum(const char* name, uint8_t CrossPointSettings::* ptr, std::vector<std::string> values) {
+    return {name, SettingType::ENUM, ptr, std::move(values)};
+  }
+
+  static SettingInfo Action(const char* name) { return {name, SettingType::ACTION, nullptr}; }
+
+  static SettingInfo Value(const char* name, uint8_t CrossPointSettings::* ptr, const ValueRange valueRange) {
+    return {name, SettingType::VALUE, ptr, {}, valueRange};
+  }
 };
 
 class SettingsActivity final : public ActivityWithSubactivity {