Update Docker and pnpm fetch to be more aligned and link to each other

[segevfiner]

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[vercel]

@segevfiner is attempting to deploy a commit to the pnpm Team on Vercel.

A member of the Team first needs to authorize it.

[segevfiner]

I also added a more complex Dockerfile example that combines all the techniques.

[segevfiner]

Also it is likely a user will want a .dockerignore/Dockerfile.dockerignore, e.g.

**/node_modules
**/dist

Though there are likely additional patterns he might want. We can add that to the docs as well.