Add submodule recursion for `github/lab_repo` rule

[cemeceme]

Currently, the built in rules for fetching repositories from github and gitlab will fetch a zip archive from the server, unzip it and apply some optional modifications. However, this method does not make it possible to also fetch any submodules that a git repo might use.

In a perfect world, all projects would use please and this not have an issue when fetching further dependencies, however please is not that popular and thus there are many cases where the built in rules need to put in some extra legwork to allow for compatibility with the non-please world.