Add N&N for disabled image descriptor API

N&N for eclipse-platform/eclipse.platform.ui#4094

Author: HeikoKlare

news/4.41/platform_isv.md

@@ -2,10 +2,19 @@
 
 A special thanks to everyone who [contributed to Eclipse-Platform](acknowledgements.md#eclipse-platform) or [contributed to Equinox](acknowledgements.md#equinox) in this release!
 
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 ## Platform Changes
--->
+
+### Shared Disabled Image Descriptor on `ImageDescriptor`
+
+<details>
+<summary>Contributors</summary>
+
+- [Heiko Klare](https://github.com/HeikoKlare)
+</details>
+
+`ImageDescriptor` now provides `asDisabledDescriptor()`, which returns a lazily created, shared `ImageDescriptor` for the disabled version of the image.
+This allows you to use a single descriptor with a `ResourceManager` to share both the original and disabled images, instead of managing two independent descriptors.
 
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