Create config.yml

[Dargon789]

Summary by Sourcery

Add initial CircleCI configuration to enable automated builds using a custom Docker executor and a defined workflow.

Build:

• Add .circleci/config.yml with version 2.1 specification and custom Docker executor.

CI:

• Define web3-defi-game-project job with checkout step.
• Set up my-custom-workflow to run the job.