Support usage __outside__ of a monorepo

[hamlim]

If I have a plain-old repo (e.g. single package.json, no workspaces), then the tool should ideally still work as-is.

However it doesn't seem to be the case currently, if I run it in an example repo with DEBUG=one-version I get the following logs:

❯ DEBUG=one-version bun run one-version:check
$ one-version check
[one-version] Initial config {
  "$schema": "https://one-version.vercel.app/schema.json",
  "packageManager": "bun",
  "versionStrategy": "pin"
}
[one-version] Workspaces []
[one-version] Workspaces Dependencies []
[one-version] Duplicate dependencies []
[one-version] Unpinned dependencies {}
My preciousss
 ✨ One Version Rule Success - found no version conflicts!