docs(tick): simplify and promote lv_tick_set_cb

[kisvegabor]

Description of the feature or fix

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Notes

• Update the Documentation if needed.
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[LeCyberDucky]

In case you also want an example for the ESP32 (since you have the STM32 example), I think this should do the trick:
lv_tick_set_cb([]-> uint32_t{ return esp_timer_get_time()/1000; });

[kisvegabor]

lv_tick_set_cb([]-> uint32_t{ return esp_timer_get_time()/1000; });

Anonymus functions are not C standard, but I pushed an update to mention esp_timer_get_time.