Fixing GitHub Actions (#27)

+ Don't run publish on PRs to master
+ Don't run publish on master

.github/workflows/build.yml

@@ -25,7 +25,7 @@ jobs:
         run: ./gradlew build --no-daemon
 
       - name: Publish
-        if: github.ref != 'refs/heads/master'
+        if: github.ref != 'refs/heads/master' && !(github.event_name == 'pull_request' && github.base_ref == 'master')
         run: ./gradlew publish --no-daemon
         env:
           SONATYPE_USERNAME: ${{ secrets.SONATYPE_USERNAME }}