🧪 Fix artifact URLs in the dumb-pypi index

Looks like migrating the GitHub Pages publishing mechanism from a Git
branch to an artifact-based process broke this. It used to point to
artifacts on the branch. Now, this patch changes it to point to the
public GH Pages URL from the static website.

Resolves #679.

Author: webknjaz

.github/workflows/ci-cd.yml

@@ -1888,9 +1888,9 @@ jobs:
       run: |
         python -m dumb_pypi.main \
           --package-list <(ls dist/) \
-          --packages-url https://raw.githubusercontent.com/${{
-            github.repository
-          }}/gh-pages/dist \
+          --packages-url "https://${{
+            github.repository_owner
+          }}.github.io/${GITHUB_REPOSITORY#$GITHUB_REPOSITORY_OWNER/}/dist" \
           --output-dir gh-pages-dumb-pypi
       shell: bash