fix: getBackgroundAudioManager 的 onPrev 和 onNext 无效的问题

src/core/service/api/context/background-audio.js

@@ -72,6 +72,8 @@ const props = [
     default: 'http'
   }
 ]
+
+const backgroundEvents = ['prev', 'next']
 
 class BackgroundAudioManager {
   constructor () {
@@ -89,6 +91,15 @@ class BackgroundAudioManager {
           } : {})
         }
       })
+    })
+    backgroundEvents.forEach((name) => {
+      onMethod(`onBackgroundAudio${name[0].toUpperCase() + name.substr(1)}`, () => {
+        callbacks[name].forEach(callback => {
+          if (typeof callback === 'function') {
+            callback({})
+          }
+        })
+      })
     })
     props.forEach(item => {
       const name = item.name