ci: push Docker images only after tests succeed

[anuragxxd]

CI pipeline from the Github Actions right now is running two jobs in parallel:

• Docker: builds Docker images and pushes to the registry
• Linting and unit tests: lints code and runs unit and integration tests

A better approach will be to run the "Docker" job only after the "Linting and unit tests" job completed successfully.

Advantages of this will be:

• Bad code won't be pushed to the image registry
• It will save resources in case of failure

[uniqueg]

Closed by #127