Update README for mcufriend support
- Includes cross-platform **GUIslice Builder** (beta) desktop application to generate layouts
- *Platform-independent GUI core currently supports*: SDL1.2, SDL2.0, Adafruit-GFX, TFT_eSPI
- *Devices*: Raspberry Pi, Arduino, ESP8266 / NodeMCU, ESP32, M5stack, Feather M0 (Cortex-M0), nRF52 (Cortex-M4F), LINUX, Beaglebone Black, STM32
-- *Typical displays*: PiTFT, Waveshare, Adafruit TFT 3.5" / 2.8" / 2.4" / 2.2" / 1.44", OLED 0.96", 4D Cape
+- *Typical displays*: PiTFT, Adafruit TFT 3.5" / 2.8" / 2.4" / 2.2" / 1.44", OLED 0.96", mcufriend, Waveshare, 4D Cape
- *Display drivers include*: ILI9341, ST7735, SSD1306, HX8357, PCD8544
- *Touchscreen control including*: STMPE610, FT6206, XPT2046, 4-wire, tslib
- Foreign characters / UTF-8 encoding (in SDL mode), anti-aliased fonts (in TFT_eSPI mode)
