Refactor(types): enhance the types of event properties

Author: wellyshen

src/use-web-animations.d.ts

@@ -19,9 +19,9 @@ declare module "@wellyshen/use-web-animations" {
   }
 
   export interface Event {
-    playState: PlayState;
+    readonly playState: PlayState;
     animate: Animate;
-    animation: Animation;
+    readonly animation: Animation;
   }
 
   export interface Callback {

src/useWebAnimations.ts

@@ -23,9 +23,9 @@ interface Animate {
 }
 interface Callback {
   (event: {
-    playState: PlayState;
+    readonly playState: PlayState;
     animate: Animate;
-    animation: Animation;
+    readonly animation: Animation;
   }): void;
 }
 export interface Options<T> extends AnimConf {