add WebSocket timers

- EventDispatcher, TimerEvent add.

common/src/main/kotlin/space/mori/chzzk_bot/common/events/EventBase.kt

@@ -0,0 +1,19 @@
+package space.mori.chzzk_bot.common.events
+
+interface Event
+
+interface EventHandler<E: Event> {
+    suspend fun handle(event: E)
+}
+
+object EventDispatcher {
+    private val handlers = mutableMapOf<Class<out Event>, MutableList<EventHandler<out Event>>>()
+
+    fun <E : Event> register(eventClass: Class<E>, handler: EventHandler<E>) {
+        handlers.computeIfAbsent(eventClass) { mutableListOf() }.add(handler)
+    }
+
+    suspend fun <E : Event> dispatch(event: E) {
+        handlers[event::class.java]?.forEach { (it as EventHandler<E>).handle(event) }
+    }
+}

common/src/main/kotlin/space/mori/chzzk_bot/common/events/TimerEvents.kt

@@ -0,0 +1,11 @@
+package space.mori.chzzk_bot.common.events
+
+enum class TimerType {
+    UPTIME, TIMER, REMOVE
+}
+
+class TimerEvent(
+    val uid: String,
+    val type: TimerType,
+    val time: String?
+): Event