feat: Add SPI support for and update README.

[eMUQI]

Summary

Adds SPI interface support for SSD1327 OLED displays

Implementation

• New SSD1327_SPI class with proper pin handling (DC, RES, CS)
• Hardware reset sequence during initialization
• Optional CS pin support for different display modules

Testing

测试了readme中的示例以及rotating_3d_cube.py，btw 在spi 接口下动画帧率明显

Tested the example in readme and rotating_3d_cube.py. BTW, the SPI interface delivers significantly higher animation frame rates.

Tested successfully on:

• ESP32-S3-ZERO + WaveShare 1.5inch OLED Module
• Raspberry Pi Pico + WaveShare 1.5inch OLED Module

Compatibility

Existing I2C implementations remain unchanged.

[eMUQI]

Hi, @mcauser ! Thanks for this great library. I needed SPI support for my project, so I implemented it and thought I'd share in case it might be useful to others. Let me know if this is something you'd consider merging – happy to make any changes or discuss alternative approaches!