Update pnpm.md with lock file info

[adrienne-fossa]

Overview

Update the pnpm documentation with a note that says that anything defined in the importers section will be ignored

Acceptance criteria

• the documentation makes sense

Testing plan

How did you validate that this PR works? What literal steps did you take when manually checking that your code works?

Example:

1. Set up test case X.
2. Run command Y. Make sure Z happens.

This section should list concrete steps that a reviewer can sanity check and repeat on their own machine (and provide any needed test cases).

Risks

Highlight any areas that you're unsure of, want feedback on, or want reviewers to pay particular attention to.

Example: I'm not sure I did X correctly, can reviewers please double-check that for me?

Metrics

Is this change something that can or should be tracked? If so, can we do it today? And how? If its easy, do it

References

Add links to any referenced GitHub issues, Zendesk tickets, Jira tickets, Slack threads, etc.

Example:

• ANE-123: Implement X.

Checklist

• I added tests for this PR's change (or explained in the PR description why tests don't make sense).
• If this PR introduced a user-visible change, I added documentation into docs/.
• If this PR added docs, I added links as appropriate to the user manual's ToC in docs/README.ms and gave consideration to how discoverable or not my documentation is.
• If this change is externally visible, I updated Changelog.md. If this PR did not mark a release, I added my changes into an ## Unreleased section at the top.
• If I made changes to .fossa.yml or fossa-deps.{json.yml}, I updated docs/references/files/*.schema.json AND I have updated example files used by fossa init command. You may also need to update these if you have added/removed new dependency type (e.g. pip) or analysis target type (e.g. poetry).
• If I made changes to a subcommand's options, I updated docs/references/subcommands/<subcommand>.md.

[spatten]

I left one comment asking what "flagged out" means. Can you clarify that?

Also, can you fill out the PR description? It doesn't have to be much, just something saying that you are adding a note to the PNPM documentation, and that this is a documentation only change.

Here's an example: #1556

[spatten]

What does "flagged out" mean? I'm assuming it means ignored, but if it does let's say that specifically

[adrienne-fossa]

@spatten thanks for letting me know. I've updated it and submitted another request.

[spatten]

Looks good to me. Thank you!