Update node from node12 to node16 (#132)

This addresses the deprecation of Node 12 in GHA (https://github.blog/changelog/2022-09-22-github-actions-all-actions-will-begin-running-on-node16-instead-of-node12/).

action.yml

@@ -7,7 +7,7 @@ inputs:
     ssh-auth-sock:
         description: 'Where to place the SSH Agent auth socket'
 runs:
-    using: 'node12'
+    using: 'node16'
     main: 'dist/index.js'
     post: 'dist/cleanup.js'
     post-if: 'always()'