Add initial set of Playwright integration tests, for testing embeds (#254)

* add first pass on playwright integration tests!
- test embed loading via localhost:9990/embed.html as well as cross-domain with embed on localhost:8020/
while RWP + data on localhost:9990/
- add --ignore-optional to most ci runs
- add playwright ci test
- add playwright and playwright-test to dev dependencies
- add 'test-start-embed' to start test harness for localhost:8020/ embed
- add 'test-start-sandbox' to start test harndess for localhost:8030/ sandbox
- add additional tests for loading with sandbox + requiresubdomainiframe, ensure 'requiresubdomainiframe' works, doesn't allow loading directly

.github/workflows/integration.yaml

@@ -0,0 +1,28 @@
+name: Playwright Integration
+
+on:
+  push:
+  pull_request:
+
+jobs:
+  playwright:
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Check out Git repository
+        uses: actions/checkout@v2
+
+      - name: Install Node.js, NPM and Yarn
+        uses: actions/setup-node@v3
+        with:
+          node-version: 18
+          cache: 'yarn'
+
+      - name: Yarn Install
+        run: yarn install --frozen-lockfile
+
+      - name: Playwright Install Browsers
+        run: yarn playwright install
+
+      - name: Playwright Run Tests
+        run: yarn run playwright test