Workspace entries in `pnpm` lockfiles fail to parse

[maxrake]

Overview

Lockfiles for workspace pnpm projects containing file: entries cause parsing failures.

How To Reproduce

Using the isildurs_bane repo:

../isildurs_bane/pnpm_workspace  1  4 on  master [?] is 📦 v1.0.0 via  v20.8.1
❯ phylum --version
phylum v5.7.3

../isildurs_bane/pnpm_workspace  1  4 on  master [?] is 📦 v1.0.0 via  v20.8.1
❯ ls -alh
total 32
drwxr-xr-x   7 maxrake  staff   224B Oct  5 11:17 .
drwxr-xr-x  24 maxrake  staff   768B Oct 19 16:10 ..
-rw-r--r--   1 maxrake  staff   1.2K Oct  5 11:17 package-lock.json
-rw-r--r--   1 maxrake  staff   336B Oct  5 11:17 package.json
-rw-r--r--   1 maxrake  staff   890B Oct  5 11:17 pnpm-lock.yaml
-rw-r--r--   1 maxrake  staff    27B Oct  5 11:17 pnpm-workspace.yaml
drwxr-xr-x   3 maxrake  staff    96B Oct  5 11:17 projects

../isildurs_bane/pnpm_workspace  1  4 on  master [?] is 📦 v1.0.0 via  v20.8.1
❯ phylum parse -t pnpm pnpm-lock.yaml
❗ Error: could not parse lockfile: pnpm-lock.yaml

Caused by:
    0: Failed to parse lockfile
    1: Dependency 'file:projects/workspace_member' is missing '/' prefix

Expected Behavior

Lockfiles created with pnpm, from workspace projects, are able to be parsed.

Additional Context

The pnpm-lock.yaml file was re-created with the package.json file by using the command pnpm install --lockfile-only --ignore-scripts and it ended up being exactly the same as the one that was already in the repo.