Add a sync examples github workflow

The reason behind this is that the E2E tests take huge resource on
Github and become more flaky when run together both with sync and async
examples. Since we're using a weak Github runner.

.github/workflows/sync_e2e.yml

@@ -0,0 +1,73 @@
+name: sync_E2E
+on:
+  # Enable manually triggering this workflow via the API or web UI
+  workflow_dispatch:
+  push:
+    branches:
+      - main
+  pull_request:
+  schedule:
+    # At 06:00 AM UTC from Monday through Friday
+    - cron:  '0 6 * * 1-5'
+
+defaults:
+  run:
+    shell: bash
+
+jobs:
+  test:
+    strategy:
+      matrix:
+        go: [stable, tip]
+        platform: [ubuntu-latest, windows-latest, macos-latest]
+    runs-on: ${{ matrix.platform }}
+    steps:
+      - name: Checkout code
+        if: matrix.go != 'tip' || matrix.platform != 'windows-latest'
+        uses: actions/checkout@v4
+      - name: Install Go
+        if: matrix.go != 'tip' || matrix.platform != 'windows-latest'
+        uses: actions/setup-go@v5
+        with:
+          go-version: 1.x
+      - name: Install Go tip
+        if: matrix.go == 'tip' && matrix.platform != 'windows-latest'
+        run: |
+          go install golang.org/dl/gotip@latest
+          gotip download
+          echo "GOROOT=$HOME/sdk/gotip" >> "$GITHUB_ENV"
+          echo "GOPATH=$HOME/go" >> "$GITHUB_ENV"
+          echo "$HOME/go/bin" >> "$GITHUB_PATH"
+          echo "$HOME/sdk/gotip/bin" >> "$GITHUB_PATH"
+      - name: Install xk6
+        if: matrix.go != 'tip' || matrix.platform != 'windows-latest'
+        run: go install go.k6.io/xk6/cmd/xk6@master
+      - name: Build extension
+        if: matrix.go != 'tip' || matrix.platform != 'windows-latest'
+        run: |
+          which go
+          go version
+
+          GOPRIVATE="go.k6.io/k6" xk6 build \
+            --output ./k6extension \
+            --with github.com/grafana/xk6-browser=.
+          ./k6extension version
+      - name: Run E2E tests
+        if: matrix.go != 'tip' || matrix.platform != 'windows-latest'
+        run: |
+          set -x
+          if [ "$RUNNER_OS" == "Linux" ]; then
+            export K6_BROWSER_EXECUTABLE_PATH=/usr/bin/google-chrome
+          fi
+          export K6_BROWSER_HEADLESS=true
+          for f in sync-examples/*.js; do
+            if [ "$f" == "sync-examples/sync_hosts.js" ] && [ "$RUNNER_OS" == "Windows" ]; then
+              echo "skipping $f on Windows"
+              continue
+            fi
+            ./k6extension run -q "$f"
+          done
+      - name: Check screenshot
+        if: matrix.go != 'tip' || matrix.platform != 'windows-latest'
+        # TODO: Do something more sophisticated?
+        run: test -s screenshot.png