[kr] Korean translation for lesson 3 sensors-and-actuators of 1-getting-started file (microsoft#410)

* Create README.kr.md

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* translate kr

* Update README.kr.md

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* Translation_kr

create assignment.kr.md

* Create pi-actuator.kr.md

[create]  pi-actuator.kr.md

* Create pi-sensor.kr.md

[create] Korean Translation of pi-sensor

* Update pi-actuator.kr.md

* Update pi-sensor.kr.md

* Update README.kr.md

fix README.KR.md

* Update README.kr.md

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* Update assignment.kr.md

Review-based modifications

* Create single-board-computer-mqtt.kr.md

This file is translated to Korean

Author: WZNT-KimHyeJin