[readme][m]: merges contributing guidelines

Author: EvgeniiaVak

CONTRIBUTING.md

@@ -75,3 +75,33 @@ We can make different queries:
 #### Query Table with Limit and Offset (pagination)
 
 ![Query Table Limit Offset](documentation/query-table-limit-offset.png)
+
+## Contributing
+
+### Local development environment
+
+1. launch bg services (postgres + hasura) (`bash run-mock-environment.sh`)
+2. `cp .env.example .env`
+3. `yarn`
+4. `yarn start` to launch server / `yarn test` to run tests
+5. install and use prettier to format code - https://prettier.io/docs/en/install.html (otherwise new builds will likely fail)
+
+Please don't forget to add new variables to `.env.example` - they also will be used in ci tests.
+
+### CI
+
+#### Tests
+
+Tests and formating check and run automatically on every push and pull request to master. They run on Docker hub. See documentation here https://docs.docker.com/docker-hub/builds/automated-testing/
+
+To simulate tests as running on dockerhub you can run `bash run-tests-in-docker.sh` file.
+
+If a pull request has failed checks it shows an error message in GitHub. The link to DockerHub does not work though.
+You will need to navigate there:
+
+- Docker repository is here https://hub.docker.com/repository/docker/datopian/data-api
+- To see build jobs go to builds https://hub.docker.com/repository/docker/datopian/data-api/builds and find your build/test
+
+#### Docker image builds
+
+After every push to master and successful tests there is a new docker image built here https://hub.docker.com/repository/docker/datopian/data-api/builds