Add a release note for scene types refactor (#20051)

Its really barebones but I'm not sure what else to write.

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Co-authored-by: Robert Swain <robert.swain@gmail.com>

Author: atlv24

release-content/release-notes/scene-type-crates.md

@@ -0,0 +1,7 @@
+---
+title: Define scenes without depending on bevy_render
+authors: ["@atlv24"]
+pull_requests: [19997, 19991, 20000, 19949, 19943, 19953]
+---
+
+It is now possible to use cameras, lights, and meshes without depending on the Bevy renderer. This makes it possible for 3rd party custom renderers to be drop-in replacements for rendering existing scenes.