fix docs and example

Author: LuisLiraC

.github/workflows/example.yaml

@@ -1,9 +1,9 @@
 name: Git Diff example
 
 on:
-  push:
+  pull_request:
     branches:
-      - example-*
+      - master
 
 jobs:
   check_diff:

README.md

@@ -56,4 +56,4 @@ jobs:
 ```
 
 > [!WARNING]
-> At this moment the action does not support branches with `/` in the name. For example, `feature/branch` will not work.
+> At this moment it only works with the `pull_request` event. It uses the `GITHUB_BASE_REF` environment variable to get the base branch of the PR and this environment variable is only available in the `pull_request` event.