Add custom config to renovate.

* Slow it down so we don't get it all at once.
* Limit to only package.json for now.

.github/renovate.json

@@ -0,0 +1,10 @@
+{
+  "extends": [
+    "config:base",
+    "schedule:weekdays"
+  ],
+  "prConcurrentLimit": 2,
+  "includePaths": [
+    "package.json"
+  ]
+}

renovate.json

@@ -1,5 +0,0 @@
-{
-  "extends": [
-    "config:base"
-  ]
-}