docs: update README to include rollout percentage options for updates

Author: floydkim

README.md

@@ -393,12 +393,15 @@ npx code-push release --framework expo --binary-version 1.0.0 --app-version 1.0.
 > [!IMPORTANT]
 > `--app-version` should be greater than `--binary-version` (SemVer comparison).
 
+- `--rollout`: The rollout percentage for the update. (0~100, inclusive)
 
 #### `update-history`
 
 Update the release history for a specific CodePush update.
 - Use the `--enable` option to disable a specific release for rollback. (or enable it)
 - Use the `--mandatory` option to make the update as mandatory or optional.
+- Use the `--rollout` option to change the rollout percentage of the update. (0~100, inclusive)
+  - If the rollout percentage is reduced, users who fall outside the new target will have their rollout canceled and rollback to the previous latest version.
 
 **Example:**
 - Rollback the CodePush update `1.0.1` (targeting the binary app version `1.0.0`).