DOC Document required permissions

README.md

@@ -8,11 +8,18 @@ This action is intended as a step in a larger workflow and at a minimum the repo
 
 **workflow.yml**
 ```yml
-steps:
-  - name: Create pull-request
-    uses: silverstripe/gha-pull-request@v1
-    with:
-      branch: pulls/4/my-branch
-      title: NEW My pull-request title
-      description: (Optional) This text will appear in the body of the GitHub pull-request
+job:
+  # ...
+  permissions:
+    contents: write
+    pull-request: write
+    actions: write
+  # ...
+  steps:
+    - name: Create pull-request
+      uses: silverstripe/gha-pull-request@v1
+      with:
+        branch: pulls/4/my-branch
+        title: NEW My pull-request title
+        description: (Optional) This text will appear in the body of the GitHub pull-request
 ```