Mention original owner and plugin ID (#971)

README.md

@@ -2,6 +2,13 @@
 
 Gradle plugin for creating fat/uber JARs with support for package relocation.
 
+> [!NOTE]\
+> Previously this plugin was developed by [@johnrengelman](https://github.com/johnrengelman) and published under the ID [`com.github.johnrengelman.shadow`](https://plugins.gradle.org/plugin/com.github.johnrengelman.shadow)
+> before maintenance was transferred to the [GradleUp organization](https://github.com/GradleUp) to ensure future development, see [#908](https://github.com/GradleUp/shadow/issues/908).
+>
+> If you are still using the old plugin ID in your build script, we recommend to switch to the new plugin ID [`com.gradleup.shadow`](https://plugins.gradle.org/plugin/com.gradleup.shadow)
+> and update to the latest version to receive all the latest bug fixes and improvements.
+
 ## Documentation
 
 Read the [User Guide](https://gradleup.com/shadow/)!

src/docs/README.md

@@ -7,6 +7,10 @@ actionText: User Guide →
 actionLink: /introduction/
 ---
 
-John Engelman - @johnrengelman
-
 [API Docs](https://gradleup.com/shadow/api/index.html)
+
+Previously this plugin was developed by [@johnrengelman](https://github.com/johnrengelman) and published under the ID [`com.github.johnrengelman.shadow`](https://plugins.gradle.org/plugin/com.github.johnrengelman.shadow)
+before maintenance was transferred to the [GradleUp organization](https://github.com/GradleUp) to ensure future development, see [#908](https://github.com/GradleUp/shadow/issues/908).
+
+If you are still using the old plugin ID in your build script, we recommend to switch to the new plugin ID [`com.gradleup.shadow`](https://plugins.gradle.org/plugin/com.gradleup.shadow)
+and update to the latest version to receive all the latest bug fixes and improvements.