Adds description of length parameter for `writeRegion()` in both head… #73

Job	Run time
compile-sketch (arduino:avr:mega, - name: arduino:avr source-url: https://downloads.arduino.cc/...	46s
compile-sketch (esp32:esp32:esp32, - name: esp32:esp32 source-url: https://raw.githubuserconten...	1m 37s
compile-sketch (esp32:esp32:esp32s2, - name: esp32:esp32 source-url: https://raw.githubusercont...	1m 33s
compile-sketch (esp32:esp32:esp32c3, - name: esp32:esp32 source-url: https://raw.githubusercont...	1m 51s
compile-sketch (SparkFun:apollo3:sfe_artemis_atp, - name: SparkFun:apollo3 source-url: https://...	1m 59s
compile-sketch (esp8266:esp8266:thingdev, - name: esp8266:esp8266 source-url: https://arduino.e...	1m 7s
compile-sketch (arduino:samd:mkr1000, - name: arduino:samd # source-url: https://downloads.ardu...	1m 5s
compile-sketch (arduino:mbed:nano33ble, - name: arduino:mbed # source-url: https://downloads.ar...	1m 30s
compile-sketch (rp2040:rp2040:sparkfun_promicrorp2040, - name: rp2040:rp2040 source-url: https:...	1m 7s
compile-sketch (STMicroelectronics:stm32:GenF4, - name: STMicroelectronics:stm32 source-url: ht...	1m 45s
	14m 20s

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