Adding support for position_ms

[UlysseM]

spotify-web-api-js/src/spotify-web-api.js

Line 1529 in 9a36af0

['context_uri', 'uris', 'offset'].forEach(function(field) {

Spotify recently added a new feature that allows to play at specific position in a track, can you add 'position_ms' in this array?

Cheers

https://developer.spotify.com/documentation/web-api/reference/player/start-a-users-playback/
spotify/web-api#596 (comment)