Fix resource configuration property (#9394)

Author: MihkelAuv

docs/reference/docfx-json-reference.md

@@ -45,7 +45,7 @@ Specifies an array of resource files to include in the project. Supports [File M
 ```json
 {
   "build": {
-    "resources": ["**/*.png"]
+    "resource": ["**/*.png"]
   }
 }
 ```

src/docfx/Models/InitCommand.cs

@@ -50,7 +50,7 @@ This utility will walk you through creating a docfx project.
                 {
                     new { files = new[] { "**/*.{md,yml}" }, exclude = new[] { "_site/**" } }
                 },
-                resources = new[]
+                resource = new[]
                 {
                     new { files = new[] { "images/**" } }
                 },