I will collect some of the required steps to add debugger support to the extension

https://code.visualstudio.com/api/extension-guides/debugger-extension

https://docs.oracle.com/javase/8/docs/jdk/api/jpda/jdi/

https://github.com/microsoft/vscode-java-debug

Probably the architecture should be VS Code -> Processing Debugger Proxy (Preprocessing) -> Java Debugger (Either VSCode native or a Java based implementation)