Improve migration guide for Sprite anchor changes (#21155)

# Objective

- #18393 could use a better migration guide.
- Fixes #21013

## Solution

- Make a table for easy CTRL+F

Author: alice-i-cecile

release-content/migration-guides/anchor_is_removed_from_sprite.md

@@ -4,3 +4,18 @@ pull_requests: [18393]
 ---
 
 The `anchor` field has been removed from `Sprite`. Instead the `Anchor` component is now a required component on `Sprite`.
+
+The anchor variants have been moved to associated constants, following the table below:
+
+| 0.16                  | 0.17                  |
+| --------------------- | --------------------- |
+| Anchor::Center        | Anchor::Center        |
+| Anchor::BottomLeft    | Anchor::BOTTOM_LEFT   |
+| Anchor::BottomCenter  | Anchor::BOTTOM_CENTER |
+| Anchor::BottomRight   | Anchor::BOTTOM_RIGHT  |
+| Anchor::CenterLeft    | Anchor::CENTER_LEFT   |
+| Anchor::CenterRight   | Anchor::CENTER_RIGHT  |
+| Anchor::TopLeft       | Anchor::TOP_LEFT      |
+| Anchor::TopCenter     | Anchor::TOP_CENTER    |
+| Anchor::TopRight      | Anchor::TOP_RIGHT     |
+| Anchor::Custom(value) | Anchor(value)         |