chore: update js doc comments to remove warnings

ember-stereo/src/-private/utils/error-cache.js

@@ -8,6 +8,7 @@ import { inject as service } from '@ember/service';
 /**
  * This class caches errors based on urls.
  * @private
+ * @class ErrorCache
  */
 
 export default class ErrorCache {

ember-stereo/src/-private/utils/evented.js

@@ -5,6 +5,7 @@ import EmberEvented from '@ember/object/evented';
  * Partial wrapper for Ember's Evented Mixin, enabling
  * a pure class-based derivation
  * @private
+ * @class Evented
  */
 export default class Evented {
   eventManager = EmberObject.extend(EmberEvented).create();

ember-stereo/src/-private/utils/metadata-cache.js

@@ -4,6 +4,7 @@ import normalizeIdentifier from './normalize-identifier';
 /**
 * This class caches metadata.
   @private
+  @class MetadataCache
 */
 
 export default class MetadataCache extends ObjectCache {

ember-stereo/src/-private/utils/object-cache.js

@@ -14,6 +14,7 @@ function isAnObject(identifier) {
 
 /**
  * This class caches things based on a strings or objects. You shouldn't have to interact with this class.
+ * @class ObjectCache
  */
 export default class ObjectCache {
   @service stereo; // used by subclasses

ember-stereo/src/-private/utils/shared-audio-access.js

@@ -15,6 +15,7 @@ const log = debug('ember-stereo:shared-audio-access');
  * worth keeping something that significantly complicates the codebase.
  *
  * @private
+ * @class SharedAudioAccess
  */
 /*
 

ember-stereo/src/-private/utils/sound-cache.js

@@ -8,11 +8,10 @@ import { inject as service } from '@ember/service';
 import { TrackedObject, TrackedArray } from 'tracked-built-ins';
 
 /**
- *
-/**
-* This class caches sound objects based on urls.
-* @private
-*/
+ * This class caches sound objects based on urls.
+ * @private
+ * @class SoundCaches
+ */
 
 export default class SoundCache {
   @service stereo;

ember-stereo/src/-private/utils/sound-proxy.js

@@ -8,6 +8,7 @@ import { registerDestructor } from '@ember/destroyable';
 /**
 * This class lazy loads sounds based on identifiers
   @private
+  @class SoundProxy
 */
 
 export default class SoundProxy extends Evented {

ember-stereo/src/-private/utils/untracked-object-cache.js

@@ -10,6 +10,8 @@ function isAnObject(identifier) {
 
 /**
  * This class caches things based on a strings or objects. You shouldn't have to interact with this class.
+ * @private
+ * @class UntrackedObjectCache
  */
 export default class UntrackedObjectCache {
   objectCache = new WeakMap();

ember-stereo/src/-private/utils/url-cache.js

@@ -4,6 +4,7 @@ import ObjectCache from './object-cache';
 /**
 * This class caches url resolutions.
   @private
+  @class UrlCache
 */
 
 export default class UrlCache extends ObjectCache {

ember-stereo/src/services/stereo.js

@@ -1109,8 +1109,11 @@ export default class Stereo extends Service.extend(EmberEvented) {
 
   /**
    * Updates now playing info from metadata if appropriate keys exist
-   */
+   * @method _updateNowPlaying
+   * @param {Object} sound
+   * @private
 
+   */
   _updateNowPlaying(sound) {
     if (!sound) return;
     if (sound.isDestroyed) return;