Update Renovate config (#1649)

* Update `config:base` to `config:recommended` (rename)
* Schedule on every Sunday
* Group all GitHub Actions deps in a single PR
* Ignore issue moderator, since we'll manually update it (possibly with config changes)
* Include and exclude Gradle dependencies (will enable ktlint individually in the future)
* Include Gradle itself (Gradle Wrapper)

.github/renovate.json

@@ -1,8 +1,21 @@
 {
   "extends": [
-    "config:base"
+    "config:recommended"
   ],
+  "schedule": ["every sunday"],
   "includePaths": [
+    "gradle/**",
     ".github/**"
+  ],
+  "ignoreDeps": ["keiyoushi/issue-moderator-action"],
+  "packageRules": [
+    {
+      "matchManagers": ["github-actions"],
+      "groupName": "{{manager}} dependencies"
+    },
+    {
+      "matchManagers": ["gradle"],
+      "enabled": false
+    }
   ]
 }