feat: fix CI to restrict semantic-release to master branch pushes only (#64)

Author: Copilot

.github/workflows/release.yml

@@ -45,6 +45,7 @@ jobs:
           node-version: 20
 
       - name: Semantic Release
+        if: github.event_name == 'push' && github.ref == 'refs/heads/master'
         run: |
           npm install -g @conveyal/maven-semantic-release semantic-release
           semantic-release --prepare @conveyal/maven-semantic-release --publish @semantic-release/github,@conveyal/maven-semantic-release --verify-conditions @semantic-release/github,@conveyal/maven-semantic-release --verify-release @conveyal/maven-semantic-release