add actorless websocket echo example

websockets/echo-actorless/README.md

@@ -0,0 +1,26 @@
+# Echo WebSocket (actor-less)
+
+Simple echo websocket server using [`actix-ws`].
+
+## Usage
+
+### Server
+
+```sh
+cd websockets/echo-actorless
+cargo run
+# starting HTTP server at http://localhost:8080
+```
+
+### Web Client
+
+Go to <http://localhost:8080/> in a browser.
+
+### CLI Client
+
+```sh
+# using `websocat` (https://github.com/vi/websocat)
+websocat -v --ping-interval=2 ws://127.0.0.1:8080/ws
+```
+
+[`actix-ws`]: https://crates.io/crates/actix-ws