fix wrong documentation preview link in readme #25

Job	Run time
build-aem-firmware / build-firmware	5m 3s
build-bba1-firmware / build-firmware	5m 16s
build-bba2-firmware / build-firmware	5m 8s
build-dada-firmware / build-firmware	4m 59s
build-mk2-firmware / build-firmware	4m 51s
build-str-firmware / build-firmware	5m 1s
build-v1-firmware / build-firmware	5m 0s
build-v2-firmware / build-firmware	5m 5s
	40m 23s

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