[unity] Fixed Timeline track displaying `None` as SkeletonAnimation reference on Unity 2020.1+. Fixed by increasing minimum Timeline dependency version to 1.2.10 (still compatible with the same Unity versions), as this issue shows only until 1.2.9. Closes #1855.

spine-unity/Modules/com.esotericsoftware.spine.timeline/package.json

@@ -10,7 +10,7 @@
 		"url": "http://esotericsoftware.com/"
 	},
 	"dependencies": {
-		"com.unity.timeline": "1.0.0"
+		"com.unity.timeline": "1.2.10"
 	},
 	"keywords": [
 		"spine",