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'

src/main.ts

@@ -1,4 +1,5 @@
 import * as core from '@actions/core';
+import * as exec from '@actions/exec';
 import * as installer from './installer';
 import fs from 'fs';
 import * as auth from './authutil';
@@ -39,6 +40,17 @@ export async function run() {
       await installer.getNode(version, stable, checkLatest, auth, arch);
     }
 
+    // Output version of node is being used
+    let installedVersion = '';
+    await exec.exec('node', ['--version'], {
+      listeners: {
+        stdout: data => {
+          installedVersion += data.toString();
+        }
+      }
+    });
+    core.setOutput('node-version', installedVersion);
+
     const registryUrl: string = core.getInput('registry-url');
     const alwaysAuth: string = core.getInput('always-auth');
     if (registryUrl) {