Add getNextSong() to API

[lebanggit]

Issue Description

Sometimes I want o know next song that i can pre/background-processing.

ex: Preload media file for smooth playing.

Expected Behavior

Add to public API

Steps To Reproduce

I saw this code to get it

https://github.com/serversideup/amplitudejs/blob/65a072dace2d4a56e65fb78d57afc8d4f37465d6/src/utilities/audioNavigation.js#L100-L151

And mannual function my our:

function getNextSong() {
    if(typeof Amplitude == 'undefined') return;
    let config = Amplitude.getConfig();
    if (config.repeat_song) {
      /*
        If the playlist is shuffled, get the now playing index.
      */
      if (config.shuffle_on) {
        nextIndex = config.shuffle_list[config.active_index].index;
        nextSong = config.shuffle_list[nextIndex];
      } else {
        nextIndex = config.active_index;
        nextSong = config.songs[nextIndex];
      }
    } else {
      /*
        If the shuffle is on, we use the shuffled list of
        songs to determine our next song.
      */
      if (config.shuffle_on) {
        /*
          If the active shuffle index + 1 is less than the length, then
          we use the next shuffle otherwise we go to the beginning
          of the shuffle list.
        */
        if (parseInt(config.active_index) + 1 < config.shuffle_list.length) {
          /*
            Set the next index to be the index of the song in the shuffle list.
          */
          nextIndex = parseInt(config.active_index) + 1;
        } else {
          nextIndex = 0;
          endOfList = true;
        }

        nextSong = config.shuffle_list[nextIndex];
      } else {
        /*
          If the active index + 1 is less than the length of the songs, then
          we use the next song otherwise we go to the beginning of the
          song list.
        */
        if (parseInt(config.active_index) + 1 < config.songs.length) {
          nextIndex = parseInt(config.active_index) + 1;
        } else {
          nextIndex = 0;
          endOfList = true;
        }

        /*
          Sets the next index.
        */
        nextSong = config.songs[nextIndex];
      }
    }
    
    return nextSong;
}

AmplitudeJS Version

5.3.2

Browser Information

No response

Link To Where Your Issue Can Be Reproduced

No response

Anything else?

No response