fix(core): export animation classes required for Renderer impl (#14002)

Closes #14001

modules/@angular/core/src/animation/animation_keyframe.ts

@@ -8,6 +8,9 @@
 
 import {AnimationStyles} from './animation_styles';
 
+/**
+ * @experimental
+ */
 export class AnimationKeyframe {
   constructor(public offset: number, public styles: AnimationStyles) {}
 }

modules/@angular/core/src/animation/animation_styles.ts

@@ -6,6 +6,9 @@
  * found in the LICENSE file at https://angular.io/license
  */
 
+/**
+ * @experimental
+ */
 export class AnimationStyles {
   constructor(public styles: {[key: string]: string | number}[]) {}
 }

modules/@angular/core/src/core.ts

@@ -35,4 +35,6 @@ export * from './core_private_export';
 export * from './animation/metadata';
 export {AnimationTransitionEvent} from './animation/animation_transition_event';
 export {AnimationPlayer} from './animation/animation_player';
+export {AnimationStyles} from './animation/animation_styles';
+export {AnimationKeyframe} from './animation/animation_keyframe';
 export {Sanitizer, SecurityContext} from './security';