generate source and javadoc jar in mavenrepo

[maxandersen]

so jreleaser will more likely "just work"

[maxandersen]

also make sure these fields are stubbed out:

<licenses>
		<license>
			<name>Apache License, Version 2.0</name>
			<url>https://www.apache.org/licenses/LICENSE-2.0.txt</url>
		</license>
	</licenses>
	<developers>
		<developer>
			<id>duke</id>
			<name>Duke</name>
			<email>[email protected]</email>
		</developer>
	</developers>
	<description>Awesome App</description>
	<scm>
	</scm>
	<url>https://xam.dk</url>

add //LICENSE <spdx> or --license on export