Update README

README.md

@@ -5,7 +5,14 @@ This project is the source for [scala-sbt.org](https://www.scala-sbt.org). It ge
 
 See [contributors](https://github.com/sbt/website/graphs/contributors) for the list of documentation contributors.
 
-## Attention plugin authors
+### Note to contributors
+
+1. `develop` branch controls **[the landing page](https://www.scala-sbt.org/)** and **[sbt 2.x docs](https://www.scala-sbt.org/2.x/docs/en/)**
+2. `1.x` branch controls the **[sbt 1.x docs](https://www.scala-sbt.org/1.x/docs/)**
+
+We welcome contributions, but we require [Scala Contributor License Agreement](https://contribute.akka.io/contribute/cla/scala) (Scala CLA), which transfers copyright to EPFL.
+
+### Attention plugin authors
 
 The source for [Community plugins](https://www.scala-sbt.org/release/docs/Community-Plugins.html) page is at [src/reference/01-General-Info/02-Community-Plugins.md](https://github.com/sbt/website/edit/develop/src/reference/01-General-Info/02-Community-Plugins.md).
 Add your plugin to this page and send us a pull request if your plugin is not already on it.