chore: setup mergify and test pr workflow

.mergify.yml

@@ -0,0 +1,18 @@
+# see:
+#  - https://docs.mergify.com/getting-started/
+pull_request_rules:
+  - name: automatic approve dependabot pull requests
+    conditions:
+      - 'author~=dependabot[bot]|dependabot-preview[bot]|dependabot'
+    actions:
+      review:
+        type: APPROVE
+
+  - name: automatic merge dependabot pull requests
+    conditions:
+      - 'author~=dependabot[bot]|dependabot-preview[bot]|dependabot'
+      - '#approved-reviews-by>=1'
+      - 'base=main'  # replace 'main' with the name of the branch you want to auto-merge into
+    actions:
+      merge:
+        method: merge