Add guard to publish workflow to skip on forks.

Author: alexrudy

.github/workflows/publish.yml

@@ -13,6 +13,7 @@ jobs:
   publish:
     name: Publish to crates.io
     runs-on: ubuntu-latest
+    if: ${{ github.repository_owner == 'alexrudy' }}
     steps:
       - name: Checkout
         uses: actions/checkout@v4