chore: update version in README (#8)

Author: jasikpark

README.md

@@ -43,7 +43,7 @@ Basic Usage
 ```yaml
 steps:
   - name: Waiting for Netlify Preview
-    uses: kamranayub/wait-for-netlify-action@2.0.0
+    uses: kamranayub/wait-for-netlify-action@v2.1.0
     id: wait-for-netflify-preview
     with:
       site_name: "YOUR_SITE_NAME"
@@ -78,7 +78,7 @@ jobs:
         run: |
           npm run build
       - name: Waiting for 200 from the Netlify Preview
-        uses: kamranayub/wait-for-netlify-action@2.0.0
+        uses: kamranayub/wait-for-netlify-action@v2.1.0
         id: wait-for-netflify-preview
         with:
           site_name: "YOUR_SITE_NAME"