Add CI tests

[mkopcins]

We should have CI testing, includes native code tests (gtest or similar), hf model testing (this can be done periodically to lower costs), JSI layer tests and perhaps example apps test

[msluszniak]

Basic setup with gtest is implemented in this PR which is ready for review: #438, CI, demo apps, hf and jsi to go ;)

[msluszniak]

Correct me if I'm wrong, but this issue should be added to the milestone for release 1.0.0. On a roadmap, there is an entry called: "Comprehensive testing setup". There is no other issue related to the testing infrastructure. So I'm adding this one to the mentioned milestone.