add mergify config

.mergify.yml

@@ -0,0 +1,17 @@
+pull_request_rules:
+
+  - name: warn on conflicts
+    conditions:
+      - conflict
+    actions:
+      comment:
+        message: This pull request is now in conflict... :(
+
+  - name: add core reviewer
+    conditions:
+      # number of review approvals
+      - "#approved-reviews-by<3"
+    actions:
+      request_reviews:
+        users:
+          - Borda