chore(action): add branding to action.yml (#10)

- Introduced `branding` metadata to `action.yml`.
- Set the `icon` to `loader` and the `color` to `purple`.
- Enhances the visual representation of the action on the GitHub Actions marketplace.

Author: warnyul

action.yml

@@ -53,4 +53,6 @@ runs:
           sh action.sh
         post: |
           sh post_action.sh
-
+branding:
+  icon: loader
+  color: 'purple'