introduce first Renovate configuration

Introduce pretty basic first Renovate configuration with a package rule
for grouping all stable non-major dependency updates together.

renovate.json

@@ -0,0 +1,24 @@
+{
+  "$schema": "https://docs.renovatebot.com/renovate-schema.json",
+  "extends": [
+    "config:recommended", // Included in config:best-practices anyway, but added for clarity.
+    "config:best-practices",
+    "schedule:daily",
+    ":ignoreUnstable"
+  ],
+  "packageRules": [
+    // Create a package rule for grouping all stable non-major dependency updates together.
+    // A combination of/inspired by:
+    // https://docs.renovatebot.com/presets-group/#groupallnonmajor
+    // https://docs.renovatebot.com/presets-default/#automergestablenonmajor
+    {
+      "groupName": "all stable non-major dependencies",
+      "groupSlug": "all-stable-minor-patch",
+      "matchCurrentVersion": "!/^0/",
+      "matchUpdateTypes": [
+        "minor",
+        "patch"
+      ]
+    }
+  ]
+}