Debug the source TypeScript code of locally built NPM module using VS Code

I have a Node.js application (A) written in TypeScript, which references another NPM module (M), also written in TypeScript.

I want to use Visual Studio Code to debug the TypeScript code of M when executed in the context of A.

I already downloaded the code of M, rebuilt it locally and referenced it in A using local path, e.g.

{
  "name": "A",
  "dependencies": {
    "M": "file:../M/m.tgz"
  }
}

But when I start debugging A, all I can debug is the output JavaScript code for M (which is kind of expected, as the tgz file will contain only the transpiled JavaScript code.

How can I configure the projects to debug the TypeScript code of M instead of the JavaScript code?