in release workflow, base commit on upstream main

.github/workflows/release.yml

@@ -69,9 +69,14 @@ jobs:
           GIT_USER_EMAIL="$(git log -1 --pretty=format:'%ae')"
 
           cd typst-packages
+
+          # Add upstream remote and fetch
+          git remote add upstream https://github.com/typst/packages.git
+          git fetch --depth 1 upstream main
+
           git config user.name "${GIT_USER_NAME}"
           git config user.email "${GIT_USER_EMAIL}"
-          git checkout -b "${PKG_NAME}-${PKG_VERSION}"
+          git checkout --no-track -B "${PKG_NAME}-${PKG_VERSION}" upstream/main
           git add .
           git commit -m "${PKG_NAME}:${PKG_VERSION}"
           git push --force --set-upstream origin "${PKG_NAME}-${PKG_VERSION}"