add flatpak repo

Hopefully this works

.github/workflows/flatpak.yml

@@ -35,3 +35,60 @@ jobs:
               with:
                   name: flatpak-${{ matrix.arch }}
                   path: result/nexus.federated.nexus.flatpak
+
+    publish:
+        needs: build-flatpak
+        if: github.ref == 'refs/heads/main'
+        runs-on: ubuntu-latest
+        permissions:
+            pages: write
+            id-token: write
+        environment:
+            name: github-pages
+            url: ${{ steps.deployment.outputs.page_url }}
+        steps:
+            - name: Install flatpak tooling
+              run: sudo apt-get update && sudo apt-get install -y flatpak ostree
+
+            - name: Download bundles
+              uses: actions/download-artifact@v7
+              with:
+                  pattern: flatpak-*
+                  path: bundles
+
+            - name: Build OSTree repo
+              run: |
+                  ostree init --repo=repo --mode=archive-z2
+                  for bundle in bundles/*/nexus.federated.nexus.flatpak; do
+                    flatpak build-import-bundle repo "$bundle"
+                  done
+                  flatpak build-update-repo --prune repo
+
+            - name: Assemble site
+              run: |
+                  mkdir site
+                  cp -a repo/. site/
+
+                  cat > site/nexus.flatpakrepo <<EOF
+                  [Flatpak Repo]
+                  Title=Nexus
+                  Url=https://nexus.federated.nexus/flatpak/
+                  EOF
+
+                  cat > site/nexus.flatpakref <<EOF
+                  [Flatpak Ref]
+                  Title=Nexus
+                  Name=nexus.federated.nexus
+                  Url=https://nexus.federated.nexus/flatpak/
+                  SuggestRemoteName=nexus
+                  IsRuntime=false
+                  RuntimeRepo=https://dl.flathub.org/repo/flathub.flatpakrepo
+                  EOF
+
+            - uses: actions/upload-pages-artifact@v4
+              with:
+                  path: site
+
+            - name: Deploy to Pages
+              id: deployment
+              uses: actions/deploy-pages@v4