docs: document writing_changes in the Github action

docs/github-action.md

@@ -32,13 +32,23 @@ jobs:
       with: 
         files: ./file.txt
         isolated: true
+
+    - name: Writes changes in the local checkout
+      uses: crate-ci/typos@master
+      with: 
+        write_changes: true
 ```
 
 **Important** for any of the examples above, make sure that you choose
 a release or commit as a version, and not a branch (which is a moving target).
+
 Also make sure when referencing relative file paths to use `./` (e.g., `./file.txt` instead of
 `file.txt`.
 
+`write_changes` doesn't commit or push anything to the branch. It only writes the changes locally
+to disk, and this can be combined with other actions, for instance that will [submit code
+suggestions based on that local diff](https://github.com/getsentry/action-git-diff-suggestions).
+
 ## Variables
 
 | Name | Description | Required | Default |
@@ -46,3 +56,4 @@ Also make sure when referencing relative file paths to use `./` (e.g., `./file.t
 | files| Files or patterns to check | false | If not defined, entire repository is checked |
 | isolated | Ignore implicit configuration files | false | false|
 | config | Use a custom config file (must exist) | false | not set |
+| write_changes | Writes changes on the Action's local checkout | false | false |