Point to toolkit docs

Author: Danny McCormick

README.md

@@ -1,3 +1,5 @@
 # Node 12 Template Action
 
-To get started, click the `Use this template` button on this repository [which will create a new repository based on this template](https://github.blog/2019-06-06-generate-new-repositories-with-repository-templates/).
+To get started, click the `Use this template` button on this repository [which will create a new repository based on this template](https://github.blog/2019-06-06-generate-new-repositories-with-repository-templates/).
+
+For info on how to build your first JavaScript action, see the [toolkit docs folder](https://github.com/actions/toolkit/blob/master/docs/node12-action.md).