Change to single quotes for runs syntax

fixes dev-drprasad#18 this and the previous commit dev-drprasad@7813493
Just in case there's some weird escaping happening, but likely not? 
Following the convention used in GitHub Docs examples https://docs.github.com/en/actions/creating-actions/metadata-syntax-for-github-actions#runs-for-javascript-actions
such as:
```yaml
runs:
  using: 'node16'
  pre: 'setup.js'
  main: 'index.js'
  post: 'cleanup.js'
```

Author: thadguidry

action.yml

@@ -19,5 +19,5 @@ inputs:
     required: false
 
 runs:
-  using: "node16"
-  main: "index.js"
+  using: 'node16'
+  main: 'index.js'