Support pushing to test pypi on every push.

This tests the build and deployment process much more often.

.github/workflows/release.yml

@@ -1,6 +1,11 @@
 name: Publish Python 🐍 distribution 📦 to PyPI and TestPyPI
 
-on: push
+on:
+  push:
+    # For the main branch only.
+    branches:
+      - main
+    workflow_dispatch:
 
 env:
   PYPI_URL: https://pypi.org/p/django-debug-toolbar
@@ -95,7 +100,7 @@ jobs:
 
   publish-to-testpypi:
     name: Publish Python 🐍 distribution 📦 to TestPyPI
-    if: startsWith(github.ref, 'refs/tags/')  # only publish to TestPyPI on tag pushes
+    # Always publish to TestPyPI on every push to main.
     needs:
     - build
     runs-on: ubuntu-latest