Feature request: Partial upload/deploy

TLDR: Can this Action support this workflow natively?

My project currently uses this configuration to publish to GitHub Pages from the main branch:

      - name: Upload Cargo doc output to GitHub Pages
        uses: actions/upload-pages-artifact@v3
        with:
          path: target/doc
  deploy:
    name: Deploy to GitHub Pages
    environment:
      name: github-pages
      url: ${{ steps.deployment.outputs.page_url }}
    runs-on: ubuntu-latest
    needs: build
    steps:
      - name: Deploy to GitHub Pages
        id: deployment
        uses: actions/deploy-pages@v4

This generates rustdoc and then uploads the generated files to GitHub Pages.

I'm hoping to extend our GitHub pages to also upload a copy of the generated rustdoc for each in-flight PR so that we can preview what the docs will look like. I believe this should be possible with only a small addition to this Action: namely, the ability to specify a target subdirectory when deploying an artifact. This should in theory only require one extra input to the Action:

    steps:
      - name: Deploy to GitHub Pages
        id: deployment
        uses: actions/deploy-pages@v4
        target: a/b/c

The target input would be optional, and default to .. It would instruct the Action to overwrite not necessarily the entire deployment, but a specific subdirectory of the deployment. This would allow us to write something like:

    steps:
      - name: Deploy to GitHub Pages
        id: deployment
        uses: actions/deploy-pages@v4
        target: pulls/${{ ... }}

...and invoke this from a workflow triggered by each PR.

Start with the .github/workflows/docs.yml example to understand the existing upload and deploy flow. Investigate the deploy-pages action entry point and how its inputs are handled; done means an optional target can update a deployment subdirectory without overwriting the rest, enabling per-PR documentation previews.