Add missing FreeRTOS header inclusion that cause compilation errors (GIT8266O-583)

[midnight-wonderer]

Another missing header.
I've got

In file included from /home/me/esp/ESP8266_RTOS_SDK/components/esp8266/include/driver/uart.h:25:0,
                 from main.c:1:
/home/me/esp/ESP8266_RTOS_SDK/components/freertos/include/freertos/queue.h:33:3: error: #error "include FreeRTOS.h" must appear in source files before "include queue.h"

Adding what suggested and the compilation passed.
This is because queue.h uses something that defines in FreeRTOS.h

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