chore: add mergify auto-merge for renovate (#780)

Author: trim21

.github/mergify.yml

@@ -6,3 +6,19 @@ pull_request_rules:
       label:
         toggle:
           - conflict
+
+  - name: Automatic merge on approval
+    conditions:
+      - "#commits-behind=0"
+      - or:
+          - "#approved-reviews-by>=1"
+          - label=ci:auto-merge
+      - not:
+          and:
+            - "head*=renovate/lockfile-maintenance-*"
+            - "created-at>24h ago"
+      - base=master
+      - check-success=build
+    actions:
+      merge:
+        method: squash

.github/renovate.json

@@ -18,5 +18,10 @@
   ],
   "separateMajorMinor": false,
   "updateNotScheduled": false,
-  "rangeStrategy": "bump"
+  "rangeStrategy": "bump",
+  "labels": [
+    "ci:auto-merge",
+    "dependencies"
+  ],
+  "prConcurrentLimit": 3
 }