Improve docs (ueman#130)

* Mark files which are not exposed to the user as such

* Enable public_member_api_docs Lint

* Improve documentation

* update version

fix license again

fix license

fix license

improve docs (ueman#128)

* improve docs

* update pubspec.yml

stable feedback 2.1.0

fix feedback_sentry pubspec.yaml

update feedback_gitlab changelog and version

Remove Dependency

stable 2.0.0