This PR adds node-version to the action output.

This is present in e.g. setup-python
https://github.com/actions/setup-python/blob/main/action.yml

closes #150

action.yml

@@ -30,6 +30,8 @@ inputs:
 outputs:
   cache-hit: 
     description: 'A boolean value to indicate if a cache was hit.'
+  node-version:
+    description: 'The installed node version.'
 runs:
   using: 'node16'
   main: 'dist/setup/index.js'