Copy docs into Zeek repo directly

This is based on commit 99e6942efec5feff50523f6b2a1f5868f19ab638 from the
zeek-docs repo.

doc/devel/websocket-api/server.zeek

@@ -0,0 +1,15 @@
+global hello: event(c : count);
+
+global c = 0;
+
+event tick()
+	{
+	Cluster::publish("zeek.bridge.test", hello, ++c);
+	schedule 1.0sec { tick() };
+	}
+
+event zeek_init()
+	{
+	Cluster::listen_websocket([$listen_addr=127.0.0.1, $listen_port=8000/tcp]);
+	event tick();
+	}