Add catch up behavior to xTaskDelayUntil.

Adds an explanation for why xTaskDelayUntil
can break from the configured frequency when
catching up for past events. More will be added
to the website documentation.

Author: kstribrnAmzn

include/task.h

@@ -897,7 +897,8 @@ void vTaskDelay( const TickType_t xTicksToDelay ) PRIVILEGED_FUNCTION;
  *
  * @return Value which can be used to check whether the task was actually delayed.
  * Will be pdTRUE if the task way delayed and pdFALSE otherwise.  A task will not
- * be delayed if the next expected wake time is in the past.
+ * be delayed if the next expected wake time is in the past. This prevents periodic
+ * tasks from accumulating delays and allows them to resume their regular timing pattern.
  *
  * Example usage:
  * @code{c}