Small fixes I found while integrating with GeckoView
Fixes #21: Add apiLint to tasks.check.
Add group to apiLint and apiUpdate.
This makes the tasks show up when calling gradle tasks.
Fixes #20: Don't add apidoc-plugin dependency twice.
When running the apiLint command on multiple targets (e.g. on debug and
release), apiLint fails because the dependency is added twice.
Small fixes I found while integrating with
GeckoViewapiLintandapiUpdate. This makes the tasks show up when callinggradle tasks.apiLintcommand on multiple targets (e.g. ondebugandrelease),apiLintfails because the dependency is added twice.