build: recommend Xcode 13 or later

Change-Id: I8d3d48baa8bff7b2f36cb9371d5deb62c4a079db
diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index d3110a4..14a5425 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -1,6 +1,8 @@
 name: CI
 on:
   push:
+    branches:
+      - '**'
   workflow_dispatch:
 
 permissions: {}