Tasks to build source and javadoc jars with gradle

build.gradle.kts

tasks.register<Jar>("sourcesJar") {
    archiveClassifier.set("sources")
    from(sourceSets.main.get().allJava)
}

tasks.register<Jar>("javadocJar") {
    archiveClassifier.set("javadoc")
    from(tasks.javadoc.get().destinationDir)
}