New: Add TMDB ID support

Closes #6866

src/NzbDrone.Core/MetadataSource/SkyHook/Resource/ShowResource.cs

@@ -23,6 +23,7 @@ namespace NzbDrone.Core.MetadataSource.SkyHook.Resource
         public string LastAired { get; set; }
         public int? TvRageId { get; set; }
         public int? TvMazeId { get; set; }
+        public int? TmdbId { get; set; }
 
         public string Status { get; set; }
         public int? Runtime { get; set; }

src/NzbDrone.Core/MetadataSource/SkyHook/SkyHookProxy.cs

@@ -188,6 +188,11 @@ namespace NzbDrone.Core.MetadataSource.SkyHook
                 series.TvMazeId = show.TvMazeId.Value;
             }
 
+            if (show.TmdbId.HasValue)
+            {
+                series.TmdbId = show.TmdbId.Value;
+            }
+
             series.ImdbId = show.ImdbId;
             series.Title = show.Title;
             series.CleanTitle = Parser.Parser.CleanSeriesTitle(show.Title);