Preliminary commit for adding a doc page regarding singleton-types

Author: Varunram

docs/docs/reference/singleton-types.md

@@ -0,0 +1,39 @@
+---
+layout: doc-page
+title: "Literal Singleton Types"
+---
+
+Singleton types is one of the most popular features in Scala. Literal Singleton types takes it a step further.
+Right now, a popular way to replicate literal singleton types is to create macros and/or use libraries such as
+`shapeless` due to the lack of a syntax to express them.
+
+With Literal Singelton types, it is possible to do something like
+
+```scala
+val t: "Jedi".type = "Jedi"
+```
+or
+```scala
+val t: 42.type = 42
+```
+or
+```scala
+val t: 42 = 42
+```
+
+to use literal Singleton types. Trying to do the same in Scala produces the following error:
+```
+<console>:1: error: identifier expected but string literal found.
+val t: "Jedi".type = "Jedi"
+```
+
+Dotty provides support for using Literal Singleton types of the last format namely:
+```scala
+val t: 42 =42
+val x: "Jedi" = "Jedi"
+```
+and so on.
+
+There is a possibility to use singleton types in some contexts, but only on identifiers which points to a constant that conforms to `AnyRef`. This restriction is due to `Any` not having an eq method, which is what’s used for singleton type-equality check and pattern matching.
+
+For more details and the motivation behind the need for literal singleton types, check out [SIP-23](http://docs.scala-lang.org/sips/pending/42.type.html)

docs/sidebar.yml

@@ -27,6 +27,8 @@ sidebar:
               url: docs/reference/implicit-function-types.html
             - title: Phantom Types
               url: docs/reference/phantom-types.html
+            - title: Literal Singleton Types
+              url: docs/reference/singleton-types.html
         - title: Enums
           subsection:
             - title: Enumerations