test: End to end integrated test for call widget

WIDGET_TEST.md

@@ -0,0 +1,28 @@
+# Testing Element-Call in widget mode
+
+When running `yarn backend` the latest element-web develop will be deployed and served on `http://localhost:8081`.
+In a development environment, you might prefer to just use the `element-web` repo directly, but this setup is useful for CI/CD testing.
+
+## Setup
+
+The element-web configuration is modified to:
+
+- Enable to use the local widget instance (`element_call.url` https://localhost:3000).
+- Enable the labs features (`feature_group_calls`, `feature_element_call_video_rooms`).
+
+The default configuration used by docker-compose is in `test-container/config.json`. There is a fixture for playwright
+that uses
+
+## Running the element-web instance
+
+It is part of the existing backend setup. To start the backend, run:
+
+```sh
+yarn backend
+```
+
+Then open `http://localhost:8081` in your browser.
+
+## Basic fixture
+
+A base fixture is provided in `/playwright/fixtures/widget-user.ts` that will register two users that shares a room.