Use custom auth for changesets (#1417)

This will create changesets PRs as the user @preact-bot. See peter-evans/create-pull-request#48 (comment)

Author: developit

.github/workflows/release.yml

@@ -27,4 +27,4 @@ jobs:
       - name: Create Release Pull Request
         uses: changesets/action@master
         env:
-          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+          GITHUB_TOKEN: ${{ secrets.REPO_SCOPED_TOKEN }}