added external packages overview

davidchesnut · davidchesnut · commit 9450e4c27fae · 2017-02-01T17:33:16.000-08:00
diff --git a/reference/spfx/external-packages.md b/reference/spfx/external-packages.md
@@ -0,0 +1,9 @@
+# External packages
+
+External packages are typings provided for 3rd party packages used by the SharePoint Framework.
+
+External package | Description
+-----------------|------------
+es6-collections  |
+es6-promise      |
+whatwg-fetch     |
