Release v0.4.0

What's Changed

• Re-design existing step class by @dl1998 in #38
• Implement workflows list action by @dl1998 in #41
• Update actions/upload-artifacts step to v4 by @dl1998 in #45
• Update workflows.json schema by @dl1998 in #46
• Add special workflow name that runs by default by @dl1998 in #47
• Update Python version in Docker image by @dl1998 in #49
• Implement variables injection in the workflows configuration file by @dl1998 in #51
• Fix formatting by @dl1998 in #53
• Update version to 0.4.0 by @dl1998 in #54

Full Changelog: v0.3.0...v0.4.0