Add devcontainer.json Support for Dev Container Development

[perzeababa]

It would be highly beneficial for the VIVIDUS project to include a .devcontainer/devcontainer.json configuration to support Dev Containers in VS Code, GitHub Codespaces, and other compatible environments. This would streamline onboarding, standardize development environments, and improve contributor experience across platforms.

Proposed Features:

devcontainer.json with:

• Pre-installed Java SDK (matching VIVIDUS requirements)
• Maven setup
• Git and common CLI tools
• Optional: Pre-installed VS Code extensions (e.g., Java Extension Pack, CheckStyle, etc.)
• Optional: Docker-in-Docker support for running tests inside containers

Benefits:

• New contributors can start coding immediately without manual setup.
• Ensures all contributors use the same toolchain and dependencies, reducing "it works on my machine" issues.
• Pre-configured tools like Maven, Java, and linters improve productivity and reduce setup errors.
• Developers can test in an environment closer to CI pipelines, reducing integration issues.
• Enables cloud-based development with zero local setup.
• Works seamlessly across Windows, macOS, and Linux.

[valfirst]

@perzeababa could you please check: https://github.com/vividus-framework/vividus-sample-tests/blob/main/.devcontainer/devcontainer.json ?