Add testing to run against commits to master

.github/workflows/main.yml

@@ -3,9 +3,29 @@ name: Continuous Integration and Delivery
 on: [push]
 
 jobs:
-  run_example_site_tests:
+  run_tests_master:
+    if: github.ref == 'refs/heads/master'
+    name: Run Django-Address Tests on master
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v1
+        with:
+          ref: 'refs/heads/master'
+      - name: Set up Python 3.8.5
+        uses: actions/setup-python@v1
+        with:
+          python-version: 3.8.5
+      - name: Install dependencies
+        run: pip install -r example_site/requirements.txt
+      - name: Run tests
+        run: python example_site/manage.py test example_site/
+        env:
+          SYSTEM_ENV: GITHUB_WORKFLOW
+
+  run_tests_develop:
     if: github.ref == 'refs/heads/develop'
-    name: Run Django-Address Tests
+    name: Run Django-Address Tests on develop
     runs-on: ubuntu-latest
     steps:
       - name: Checkout
@@ -22,3 +42,4 @@ jobs:
         run: python example_site/manage.py test example_site/
         env:
           SYSTEM_ENV: GITHUB_WORKFLOW
+