Issue #1919186 by vijaycs85: Create configuration schemas for node module.

core/modules/node/config/schema/node.schema.yml

+# Schema for the configuration files of the node module.
+
+node.settings:
+  type: mapping
+  label: 'Node settings'
+  mapping:
+    items_per_page:
+      type: integer
+      label: 'Number of posts on front page'