ci: added renovate config

Signed-off-by: András Jáky <ajaky@cisco.com>

Author: akijakya

.github/renovate.json

@@ -0,0 +1,16 @@
+{
+    "$schema": "https://docs.renovatebot.com/renovate-schema.json",
+    "extends": [
+        "schedule:earlyMondays",
+        ":disableDependencyDashboard"
+    ],
+    "enabledManagers": [
+        "nix"
+    ],
+    "nix": {
+        "enabled": true
+    },
+    "lockFileMaintenance": {
+        "enabled": true
+    }
+}