https_server example: Add new WSS server example

Added a new https server example with WS support which runs
* keep-alive thread to send PINGs to clients
* async message to all active WS clients
Moved the existing https-server example to a subfolder

Closes https://github.com/espressif/esp-idf/issues/5733
Closes https://github.com/espressif/esp-idf/issues/5686

examples/protocols/https_server/wss_server/README.md

@@ -0,0 +1,28 @@
+# HTTP Websocket server with SSL support
+
+This example creates a SSL server and employs a simple Websocket request handler. It demonstrates handling multiple clients from the server including:
+* PING-PONG mechanism
+* Sending asynchronous messages to all clients
+
+See the `esp_https_server` component documentation for details.
+
+Before using the example, open the project configuration menu (`idf.py menuconfig`) to configure Wi-Fi or Ethernet. See "Establishing Wi-Fi or Ethernet Connection" section in [examples/protocols/README.md](../../README.md) for more details.
+
+## Certificates
+
+You will need to approve a security exception in your browser. This is because of a self signed
+certificate; this will be always the case, unless you preload the CA root into your browser/system
+as trusted.
+
+You can generate a new certificate using the OpenSSL command line tool:
+
+```
+openssl req -newkey rsa:2048 -nodes -keyout prvtkey.pem -x509 -days 3650 -out cacert.pem -subj "/CN=ESP32 HTTPS server example"
+```
+
+Expiry time and metadata fields can be adjusted in the invocation.
+
+Please see the openssl man pages (man openssl-req) for more details.
+
+It is **strongly recommended** to not reuse the example certificate in your application;
+it is included only for demonstration.