Support custom .npmrc path

[AndreasTynell]

Hey, quick heads-up about the recent action update(4.2.0). We noticed the new behavior now pulls pnpm from whatever registry is defined in a root-level .npmrc. We rely on pipeline.npmrc to point at our internal registry instead. Could we adjust the action so that it lets us pass a custom config path? before reading the root .npmrc? That would keep the new behavior intact without breaking setups like ours.

[saair-quaderi]

v4.2.0 should probably have been a major version bump if this project is using semver Pinned it to v4.1.0 after identifying the minor bump as the culprit for breaking release pipelines

(maybe good to pin anyway with all the npm supply chain attacks these days but I guess that's another matter)