Update missing tracks (#89)

Author: justinyoo

data/tracks.json

@@ -1,4 +1,14 @@
 [
+  {
+    "songId": "30717645",
+    "title": "Snowman",
+    "artist": "Sia",
+    "album": "Everyday Is Christmas (Snowman Deluxe Edition)",
+    "trackId": "7uoFMmxln0GPXQ0AcCBXRq",
+    "trackUri": "spotify:track:7uoFMmxln0GPXQ0AcCBXRq",
+    "danceability": 0.717,
+    "valence": 0.339
+  },
   {
     "songId": "14776",
     "title": "All I Want for Christmas Is You",