create support for releases, artists, tracks, and credits

Signed-off-by: ari melody <ari@arimelody.me>

admin/http.go

@@ -34,13 +34,15 @@ func Handler() http.Handler {
         }
 
         type IndexData struct {
-            Releases    []musicModel.Release
-            Artists     []musicModel.Artist
+            Releases    []*musicModel.Release
+            Artists     []*musicModel.Artist
+            Tracks      []*musicModel.Track
         }
 
         serveTemplate("index.html", IndexData{
             Releases: global.Releases,
             Artists: global.Artists,
+            Tracks: global.Tracks,
         }).ServeHTTP(w, r)
     }))