feat: add cJSON and SQLite amalgamation source files under deps/

Add the cJSON library (cJSON.c, cJSON.h) and SQLite amalgamation
(sqlite3.c, sqlite3.h, sqlite3ext.h, shell.c) as vendored dependencies
in the deps/ directory for use by the project build system.

example/websocket_concurrent_server.wren

@@ -0,0 +1,69 @@
+// retoor <retoor@molodetz.nl>
+
+import "websocket" for WebSocket, WebSocketServer
+import "scheduler" for Scheduler
+import "timer" for Timer
+
+var port = 8080
+var clientCount = 0
+var messageCount = 0
+
+System.print("=== Concurrent WebSocket Server ===")
+System.print("Listening on ws://0.0.0.0:%(port)")
+System.print("Each client connection runs in its own fiber.\n")
+
+var server = WebSocketServer.bind("0.0.0.0", port)
+
+var handleClient = Fn.new { |ws, clientId|
+  System.print("[Client %(clientId)] Connected")
+
+  while (ws.isOpen) {
+    var msg = ws.receive()
+
+    if (msg == null) {
+      System.print("[Client %(clientId)] Connection lost")
+      break
+    }
+
+    if (msg.isClose) {
+      System.print("[Client %(clientId)] Sent close frame")
+      break
+    }
+
+    if (msg.isText) {
+      messageCount = messageCount + 1
+      var text = msg.text
+      System.print("[Client %(clientId)] Received: %(text) (total messages: %(messageCount))")
+
+      if (text == "ping") {
+        ws.send("pong")
+      } else if (text == "stats") {
+        ws.send("clients: %(clientCount), messages: %(messageCount)")
+      } else if (text == "broadcast") {
+        ws.send("broadcast not implemented in this example")
+      } else {
+        ws.send("echo: %(text)")
+      }
+    } else if (msg.isBinary) {
+      messageCount = messageCount + 1
+      System.print("[Client %(clientId)] Received binary: %(msg.bytes.count) bytes")
+      ws.sendBinary(msg.bytes)
+    }
+  }
+
+  clientCount = clientCount - 1
+  System.print("[Client %(clientId)] Disconnected (%(clientCount) clients remaining)")
+}
+
+while (true) {
+  var ws = server.accept()
+
+  if (ws != null) {
+    clientCount = clientCount + 1
+    var clientId = clientCount
+
+    Scheduler.add {
+      handleClient.call(ws, clientId)
+    }
+  }
+}