fix(ci): Run build_wheels on pull requests

Author: skbill84

.github/workflows/build_wheels.yml

@@ -64,7 +64,7 @@ jobs:
     needs: [generate_matrix]
     name: Build wheels on ${{ matrix.os }}
     runs-on: ${{ matrix.os }}
-    if: github.ref == 'refs/heads/master' || startsWith(github.ref, 'refs/tags/v')
+    if: github.event_name == 'pull_request' || github.ref == 'refs/heads/master' || startsWith(github.ref, 'refs/tags/v')
     strategy:
       matrix:
         os: ${{ fromJson(needs.generate_matrix.outputs.OSES) }}