add backlight

include/LCDDisplay.hpp

@@ -14,7 +14,8 @@ class LCDDisplay {
 
     void clear();
     void setContrast(uint8_t contrast);
+    void setBacklight(bool enabled);
     void setCursor(uint8_t row, uint8_t col);
     void writeLines(std::array<std::string, 4> lines);
     void writeSStream(std::stringstream& ss);
-};
+};