add WebSocket + ws example

[kettanaito]

• Closes add WebSocket example #103

Adds a simple example of regular WebSocket API usage + ws on the server.

• Add the basic app.
• Add integration tests.
• Add E2E tests.
  • Fix an issue where the 1s -> 2nd tab is not synced but 2nd -> 1st tab is synced. Likely a bug in the WebSocketClientManager. fix(WebSocketClientManager): use localStorage for clients persistence msw#2127
• Add the example tests to the CI.

[kettanaito]

Still having failing tests on the multi-tab message sync. The clients are kept in the localStorage but something doesn't go right. May be a poorly written test, need to investigate.