Include vendor/PDCurses to gems

Author: shugo

.github/workflows/push_gem.yml

@@ -29,6 +29,8 @@ jobs:
           egress-policy: audit
 
       - uses: actions/checkout@0ad4b8fadaa221de15dcec353f45205ec38ea70b # v4.1.4
+        with:
+          submodules: true
 
       - name: Set up Ruby
         uses: ruby/setup-ruby@cacc9f1c0b3f4eb8a16a6bb0ed10897b43b9de49 # v1.176.0