ide/vscode: add instructions for debugging external binary

@ashark you mentioned wanting to be able to debug an external binary from VS Code, with the example of working on Ark service menus, but debugging the external Dolphin executable.

I'm happy to look into it, if you can elaborate a little bit. For example:

• What are you trying to do? Why do you need to debug this way? (assume I know nothing about those projects as a developer or user)
• Which part(s) / files of Ark are being changed, and where in Dolphin might we want to debug (eg. setting a breakpoint)?
• Anything else you think pertinent to replicating the workflow so I can troubleshoot