From espressif led_strip component repository.

Version: 3.0.0

This library has been lightly modified to support async operations for both spi and rmt strip drivers.

The following files were added by FastLED:

strip_spi.h
strip_spi.cpp
strip_rmt.h
strip_rmt.cpp

== External Pixel Buffer Support ==

The RMT LED strip driver now supports optional external pixel buffers. This allows callers to provide their own pixel buffer instead of having the driver allocate one internally.

Usage:
- Set `external_pixel_buf` to `nullptr` (default) for internal allocation
- Set `external_pixel_buf` to a valid buffer pointer for external allocation
- When using external buffers, the caller is responsible for buffer management
- The driver will NOT free external pixel buffers when destroyed

Benefits:
- Allows custom memory management strategies
- Enables buffer reuse across multiple strips
- Supports specific memory alignment requirements
- Prevents unwanted memory deallocation by the driver
