nodejs: define APPSODY_DEBUG_PORT

[Kamran64]

Checklist:

• [x] Read the Code of Conduct and Contributing Guidelines.

• [x] Followed the commit message guidelines.

• [x] Stack adheres to Appsody stack structure.

Modifying an existing stack:

• [x] Updated the stack version in stack.yaml

Defines the APPSODY_DEBUG_PORT environment variable in the stack. This information will be used by other projects such as Codewind.

[sam-github]

Sure, but note that there is no way to enable the debug port in a generic nodejs app (generic meaning, started with npm start).