add datasheets for SK6812RGBX parts under doc/

- plan to make 24-bit/32-bit selectable, at least at compile-time
- FX are mostly broken since they mostly assume RGB
	- tested static & blink

README.md

@@ -15,6 +15,7 @@ The FX library is based od WS2812FX Arduino librarby by kitesurfer1404 - https:/
 Clone this repository, or add it as a submodule, to your STM32 project under the Drivers/ directory.
 
 Example:
+In main.c:
 ```
 /* Private includes ----------------------------------------------------------*/
 /* USER CODE BEGIN Includes */
@@ -30,3 +31,22 @@ int main(void)
 	/* USER CODE END 2 */
 }
 ```
+
+In your interrupt service routines:
+```
+/* USER CODE BEGIN Includes */
+#include "ws2812b.h"
+#include "ws2812b_fx.h"
+/* USER CODE END Includes */
+...
+void SysTick_Handler(void)
+{
+  /* USER CODE BEGIN SysTick_IRQn 0 */
+
+  /* USER CODE END SysTick_IRQn 0 */
+  HAL_IncTick();
+  /* USER CODE BEGIN SysTick_IRQn 1 */
+  WS2812BFX_SysTickCallback();
+  /* USER CODE END SysTick_IRQn 1 */
+}
+```