Determine if files mkdocs thinks are "unlinked" need attention

[ysuarez]

Recently when building the docs locally the mkdocs software listed these following files are not linked in the navigation section.

<snip>
INFO    -  The following pages exist in the docs directory, but are not included in the "nav" configuration:
  - placeholder.md
  - contributing/readme_template.md
  - installation/docker-download.md
  - tutorials/switch_homepage_to_twig.md
  - user-documentation/recipes/alexa_search.md 
<snip>

@eldonquijote made the following early analysis of these files.

- user-documentation/recipes/alexa_search.md is linked from the page "Extending Islandora" (aka cookbook)
- placeholder.md is practically empty
- installation/docker-download.md is empty

- tutorials/switch_homepage_to_twig.md could be linked from the Cookbook as well, although I'm not sure whether the described steps are optional, or should actually be best practice if Twig is the default templating mechanism in D8..?
- contributing/readme_template.md - unclear where that should be linked from

I am wondering if we should run a grep on some of these files to see if they are being referenced somewhere? Should some of them be deleted, ignored, or linked somewhere?

[inikolaidis]

Could the contributing/readme_template.md be linked to from the section contributing/CONTRIBUTING/#contribute-code ?

[eldonquijote]

Agree with @inikolaidis on linking contributing/readme_template.md from the section contributing/CONTRIBUTING/#contribute-code