[unity] Increased officially compatible Unity version to 2021.1.

CHANGELOG.md

@@ -77,6 +77,7 @@
 
 ### Unity
 
+* **Officially supported Unity versions are 2017.1-2021.1**.
 * **Breaking changes**
   * Removed all `Spine.Unity.AttachmentTools.SkinUtilities` Skin extension methods. These have become obsoleted and error-prone since the introduction of the new Skin API in 3.8. To fix any compile errors, replace any usage of `Skin` extension methods with their counterparts, e.g. replace occurrances of `skin.AddAttachments()` with `skin.AddSkin()`. Please see the example scene `Mix and Match Skins` on how to use the new Skin API to combine skins, or the updated old example scenes `Mix and Match` and `Mix and Match Equip` on how you can update an existing project using the old workflow. If you are using `skeletonAnimation.Skeleton.UnshareSkin()` in your code, you can replace it with `Skin customSkin = new Skin("custom skin"); customSkin.AddSkin(skeletonAnimation.Skeleton.Skin);`.
   * `Skin.GetAttachments()` has been replaced by `Skin.Attachments`, returning an `ICollection<SkinEntry>`. This makes access more consistent and intuitive. To fix any compile errors, replace any occurrances of `Skin.GetAttachments()` by `Skin.Attachments`.

spine-unity/README.md

@@ -22,7 +22,7 @@ Unity's physics components do not support dynamically assigned vertices so they
 
 ## Unity version
 
-spine-unity is compatible with Unity 2017.1-2019.4.
+spine-unity is compatible with Unity 2017.1-2021.1.
 
 ## Usage