v9.0.0.0

• Add support for ESP32-S2 (LoLin mini)
• Add true parallel multi-segment output for ESP32 devices based on development version of Neopixelbus library that already includes some of my changes (Makuna/NeoPixelBus#609 Makuna/NeoPixelBus#606).
  This feature is fully supported by ESP32 and ESP32-S2. Finally we switched to my optimized Neopixelbus fork: https://github.com/awawa-dev/NeoPixelBus
  When using multi-segments in parallel mode, both segments are perfectly in sync: the signal for both segments is generated at exactly the same time.
• Both single & multi segment mode is using live prefill processing now!
  Two frames can be render&pre-render at the same time. Pre-filling provides a back buffer mechanism with little impact on RAM: there is no need to store a full second buffer, which can be a critical issue with larger LED strips or ESP32-S2. It is synchronized with DMA buffer processing.

This shows how prefill for the second frame is started immediately while the first frame is still being rendered. It waits till DMA reports that it;s already processed part of the i2s buffer (with the first frame's data) so we can safely fill that part (with the second frame's data) and wait for the next call. Without it filling i2s buffer after the first frame is sent, can take up to few ms causing delay between frames.

• Remove SPI LEDs support.
• Switched the ESP32 from a resource-hungry real-time RMT to an I2S renderer.