developer route redirects load incorrectly on Windows

[jeffmcaffer]

What is the current behavior?

On windows many of the content pages show up as having broken links in tests/links-and-images/links-and-images.js. for example,

     Found 116 total broken links: {
      "C:/git/docs/content/actions/guides/storing-workflow-data-as-artifacts.md": {
        "free-pro-team@latest": [
          {
            "broken link": "/en/free-pro-team@latest/v3/actions/artifacts",
            "reason": "linked page not found"
          }
        ],
        "enterprise-server@2.22": [
          {
            "broken link": "/en/enterprise-server@2.22/v3/actions/artifacts",
            "reason": "linked page not found"
          }
        ]
      },

What changes are you suggesting?

Turns out that the problem is actually in the parsing of redirects from the loaded pages. path.join is used at the end of the function to compute a key. since \ is used instead of /, the key is incorrect and the redirect does not get registered.

cc: @github/docs-engineering