Create an artifact with the built web UI for each commit (#729)

Part of fixing the horrendously slow Docker build for the server edge
images.

.github/workflows/build.yml

@@ -32,6 +32,11 @@ jobs:
         uses: ./.github/actions/setup
       - name: Build Web
         run: ./bin/package-browser
+      - name: Upload Build
+        uses: actions/upload-artifact@v3
+        with:
+          name: actual-web
+          path: packages/desktop-client/build
 
   # TODO: re-enable after solving https://github.com/actualbudget/actual/issues/468
   # electron: