chore: moved back the only remaining annotation

src/main/java/ftbsc/geb/api/annotations/Listen.java

@@ -0,0 +1,29 @@
+package ftbsc.geb.api.annotations;
+
+import ftbsc.geb.api.IBus;
+import ftbsc.geb.api.IEvent;
+import ftbsc.geb.api.IEventCancelable;
+import ftbsc.geb.api.IListener;
+
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+
+/**
+ * Marks the method as a listener. Its parent must implement the {@link IListener} interface
+ * and be registered an at least one GEB instance with {@link IBus#registerListener(IListener)}.
+ * The annotated method should only take a single input value, an instance of {@link IEvent} or
+ * {@link IEventCancelable}.
+ * For the annotation to work, you must be using the GEB annotation processor or an equivalent.
+ * @since 0.1.0
+ */
+@Target(ElementType.METHOD)
+@Retention(RetentionPolicy.CLASS)
+public @interface Listen {
+	/**
+	 * @return an integer indicating priority level for the listener, defaulting to 0;
+	 * 				 a higher value means it's executed before; it may be negative
+	 */
+	int priority() default 0;
+}