migration guide for bevyengine#20427 (cursor) (bevyengine#21062)

# Objective

Fixes bevyengine#21028

## Solution
Mention types moved, and rationale

Author: janis-bhm

release-content/migration-guides/cursor-android.md

@@ -0,0 +1,13 @@
+---
+title: Move cursor-related types from `bevy_winit` to `bevy_window`
+pull_requests: [20427]
+---
+
+In an effort to reduce and untangle dependencies, cursor-related types have been moved from the `bevy_winit` crate to the `bevy_window` crate.
+The following types have been moved as part of this change:
+
+- `CursorIcon` is now located at `bevy::window::CursorIcon`.
+- `CustomCursor` is now located at `bevy::window::CustomCursor`.
+- `CustomCursorImage` is now located at `bevy::window::CustomCursorImage`.
+- `CustomCursorUrl` is now located at `bevy::window::CustomCursorUrl`.
+- on the android platform, `ANDROID_APP` is now located in it's own crate and can be found at `bevy::android::ANDROID_APP`.