Modular layouts

1. Check that _config.yml sets:

   compress_html:
     blanklines: true
   

2. Build this site using the theme commit just before merging PR #1058:

   remote_theme: just-the-docs/just-the-docs@4469f45cbd3d92c3df8da6e26ffd3c7fa86f5737
   

3. Rename _site to _site_old.

4. Build this site using the theme commit just after merging PR #1058:

   remote_theme: just-the-docs/just-the-docs@2495d3e6bb5720ae23e35caf16888f0c7f37ede0
   

5. Run the following shell command in the root directory of this site:

   diff -rEBwtb -x "*.js*" -I "published_time\|dateModified" _site_old/ _site/ > diff.txt
   

6. Check that diff.txt contains only the following:

   ???
   

7. Remove _includes/search_placeholder_custom.html.