test: PDF for nested TOCs

Author: yufeih

samples/seed/articles/toc.yml

@@ -1,5 +1,5 @@
 pdfFileName: seed.pdf
-pdfCoverPage: pdf.html
+pdfCoverPage: pdf/cover.html
 items:
 - name: Getting Started
   href: docfx_getting_started.md

samples/seed/docfx.json

@@ -66,10 +66,10 @@
   "build": {
     "content": [
       { "files": [ "**/*.yml" ], "src": "obj/api", "dest": "api" },
-      { "files": [ "**/*.yml" ], "src": "obj/apipage", "dest": "apipage" },
       { "files": [ "**" ], "src": "obj/md", "dest": "md" },
       { "files": [ "**" ], "src": "obj/apipage", "dest": "apipage" },
-      { "files": [ "articles/**/*.{md,yml}", "*.md", "toc.yml", "restapi/**", "md/**", "md2/**" ] }
+      { "files": [ "articles/**/*.{md,yml}", "*.md", "toc.yml", "restapi/**" ] },
+      { "files": [ "pdf/**" ] }
     ],
     "resource": [
       {