eventbus: make it usable and add README

examples/eventbus/some_module/some_module.v

@@ -0,0 +1,27 @@
+module some_module
+
+import (
+	eventbus
+)
+
+const (
+	eb = eventbus.new()
+)
+
+pub fn do_work(){
+	mut params := eventbus.Params{}
+	for i in 0..20 {
+		println("working...")
+		if i == 15 {
+			params.put_string("error", "CRASH!!")
+			eb.publish("error", params)
+			eb.publish("error", params)
+			return
+		}
+	}
+	
+}
+
+pub fn get_subscriber() eventbus.Subscriber {
+	return eb.subscriber
+}