Shallow Node.js checkout to enable agentic coding

[kraenhansen]

To help ground the CoPilot agent, I suggest adding a script which can be ran locally to perform a shallow checkout of the existing tests and documentation.

Drafting this as its changes to package.json conflicts with #11 and needs a rebase once that merge.

Merging this PR will:

• Add a shallow-checkout-nodejs package script performing a shallow checkout of the main nodejs/node repository into a temporary directory and copy files from "test/js-native-api", "test/node-api", "doc/api/n-api.md" into node directory of the repository root.

[legendecas]

I'm not sure if this script should live in this repository. You could shallow check-out, or fully check out the nodejs/node repo at your wish. But this is not necessary to run the test.

[kraenhansen]

I agree. I'm also uncertain where this should live 🤔 It seems important to have these files in the repo for an agent to get the context needed.

While I could maintain that script outside of the repo, I thought perhaps having it in the repo would allow others to more easily join in.