chore: update workflows to upload artifacts

.forgejo/workflows/build-site.yaml

@@ -1,5 +1,9 @@
 name: build site
 on:
+  pull_request:
+    types: [opened, synchronize, edited, reopened]
+    branches:
+      - main
   push:
     branches:
       - main
@@ -13,6 +17,7 @@ jobs:
         run: nix-build
 
       - name: Pushing site to pages branch
+        if: github.event_name == 'push' && github.ref == 'refs/heads/main'
         run: |
             git switch -C pages
             find . -mindepth 1 -maxdepth 1 ! -name '.domains'  ! -name '.git' ! -name 'result' -exec rm -rf {} +
@@ -26,3 +31,8 @@ jobs:
 
             git commit --message "Deploy site"
             git push --set-upstream origin pages --force
+        
+      - uses: actions/upload-artifact@v3
+        with:
+          name: site
+          path: ./