Rename the file io.arrow-kt.arrow-gradle-config-versioning.gradle.plugin-0.12.0-rc.5-javadoc.jar to io.arrow-kt.arrow-gradle-config-versioning.gradle.plugin-0.12.0-rc.5-javadoc.zip
Use your favourite unzip tool (WinRAR / WinZIP) to extract it, now you have a folder io.arrow-kt.arrow-gradle-config-versioning.gradle.plugin-0.12.0-rc.5-javadoc
Double click index.html will open the index page on your default web browser.