Add a github workflow that prevents PRs to main that is not comming f…

…rom dev (GEOUNED-org#92) (GEOUNED-org#93)

.github/workflows/enforce_main_pr_from_dev.yml

@@ -0,0 +1,14 @@
+name: 'Check that PR to main is coming from dev if necessary'
+
+on:
+  pull_request:
+
+jobs:
+  check_branch:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Check branch
+        if: github.base_ref == 'main' && github.head_ref != 'dev'
+        run: |
+          echo "ERROR: You can only merge to main from dev."
+          exit 1