Clone submodule

Hello,
I'm using this plugin in order to use a library in my Android app. However, this library is using git submodule, which are not initialized. It would be good to clone the necessary submodule to make it work with a different kind of library.
I think there is a simple solution, by adding [setCloneSubmodules(true)](https://archive.eclipse.org/jgit/docs/jgit-2.0.0.201206130900-r/apidocs/org/eclipse/jgit/api/CloneCommand.html#setCloneSubmodules(boolean)) when doing the actual clone. (I cannot do it myself, I have building issues)