Add hardware horizontal scrolling functionality

[ksletmoe]

Summary

Added hardware horizontal scrolling functionality to the SSD1306 display driver, enabling smooth text and graphics scrolling using the controller's built-in capabilities.

Changes Made

• New API Method: Added setHorizontalScroll() method with parameter validation and error handling
• Hardware Constants: Added SSD1306 scroll command constants (SSD1306_HORIZ_SCROLL_LEFT, SSD1306_HORIZ_SCROLL_RIGHT, SSD1306_SET_SCROLL)
• Scroll Direction Enum: Added ScrollDirection enum for Left/Right scroll options
• Complete Example: Created working scrolling example with CMakeLists.txt, demo GIF, and documentation
• Code Formatting: Improved indentation consistency throughout ssd1306.cpp

Technical Implementation

The setHorizontalScroll() method:

• Validates input parameters (page range 0-7, timeInterval 0x00-0x07)
• Returns boolean success/failure status
• Supports configurable start/end pages and scroll timing
• Handles both scroll activation and deactivation
• Handles scrolling left or right