Add notes for PR 2151.

notes/0.13.10/def-settings.markdown

@@ -0,0 +1,22 @@
+
+  [@dwijnand]: http://github.com/dwijnand
+  [2151]: https://github.com/sbt/sbt/pull/2151
+
+### Fixes with compatibility implications
+
+### Improvements
+
+- Adds `Def.settings`, which facilitates mixing settings with seq of settings. See below.
+
+### Bug fixes
+
+### `Def.settings`
+
+Using `Def.settings` it is now possible to nicely define settings as such:
+
+    val modelSettings = Def.settings(
+      sharedSettings,
+      libraryDependencies += foo
+    )
+
+[#2151][2151] by [@dwijnand][@dwijnand].