mention scala-library-next in readme (scala#112)

Author: SethTisue

README.md

@@ -48,6 +48,12 @@ The following operations are provided:
 This module is community-maintained.  If you are interested in
 participating, please jump right in on issues and pull requests.
 
+## See also: scala-library-next
+
+scala-collection-contrib's merge policy is liberal: we're happy to merge most things here, without too much review, so that people can try them out.
+
+There is now (as of October 2020) the [scala-library-next repo](https://github.com/scala/scala-library-next), which is where we decide what will actually be added to the next version of the Scala standard library. The standards for merging things there are much more conservative.
+
 ## Releasing
 
 As with other Scala standard modules, build and release infrastructure