Make commit_message optional

README.md

@@ -19,7 +19,7 @@ Add the following step at the end of your job, after other steps that might add
 ```yaml
 - uses: stefanzweifel/git-auto-commit-action@v4
   with:
-    # Required
+    # Optional but recommended, defaults to "Apply automatic changes"
     commit_message: Apply automatic changes
 
     # Optional branch to push to, defaults to the current branch

action.yml

@@ -6,7 +6,7 @@ author: Stefan Zweifel <hello@stefanzweifel.io>
 inputs:
   commit_message:
     description: Commit message
-    required: true
+    default: Apply automatic changes
   branch:
     description: Git branch name, where changes should be pushed too. Required if Action is used on the `pull_request` event
     required: false