Provide some historical context for the platform

I think it's important to mention the history behind this effort,
and also to clarify the core will still include e.g., the collections,
which are truly core to the language.

Author: adriaanm

blog/_posts/2016-11-28-spp.md

@@ -11,6 +11,14 @@ simple; let's reduce the Scala standard library to a very small core, and open
 up the decision about what popular libraries should be shipped in a "batteries
 included" distribution of Scala. This is the basic idea of the Scala Platform.
 
+The Scala Platform is the logical continuation of the modularization effort
+that began in Scala 2.11. Ultimately, the scala-library should be a small core,
+that consists of the Scala types we've come to think of as part of the language,
+such as the collections and most classes defined directly in the `scala` package.
+The modularization of xml, swing and parser combinators has made it easier for
+community maintainers to step up, and the SPP will continue opening up the
+standard library to community involvement.
+
 However, bringing many open source libraries together,
 isn't easy, nor is is it easy to ensure that these essential libraries continue
 to be developed. This is why we've come up with and proposed an initial draft of