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

playwright.config.js

@@ -0,0 +1,24 @@
+import { defineConfig } from '@playwright/test';
+export default defineConfig({
+  reporter: process.env.CI ? 'github' : 'list',
+  webServer: [
+    {
+      command: 'yarn run start-prod',
+      url: 'http://127.0.0.1:9990',
+      timeout: 120 * 1000,
+      reuseExistingServer: !process.env.CI,
+    },
+    {
+      command: 'yarn run test-start-embed',
+      url: 'http://127.0.0.1:8020',
+      timeout: 120 * 1000,
+      reuseExistingServer: !process.env.CI,
+    },
+    {
+      command: 'yarn run test-start-sandbox',
+      url: 'http://127.0.0.1:8030',
+      timeout: 120 * 1000,
+      reuseExistingServer: !process.env.CI,
+    }
+  ]
+});