feat(test): Add simple cucumber test of health check (#11)

* test: add example of cucumber execution

* test: add given tce node launched in cucumber

* test: separate health_check in then statement

* test: kill tce process at the end of the scenario

* docs: add simple readme on tests/

* chore: flatten the feature directory

* fix: terminate with SIGTERM instead of the default SIGKILL

* fix: move process termination to drop

* docs: add recommandation for gherkin vscode extension