Add application-name metadata to application layout

The following metatag will be added to `app/views/layouts/application.html.erb`

```html
<meta name="application-name" content="Name of Rails Application">
```

The `application-name` is a [standard metadata name][smn], and
compliments existing app-related metatags.

[smn]:  https://developer.mozilla.org/en-US/docs/Web/HTML/Element/meta/name

Author: stevepolitodesign

railties/CHANGELOG.md

@@ -1,3 +1,13 @@
+*   Add `application-name` metadata to application layout
+
+    The following metatag will be added to `app/views/layouts/application.html.erb`
+
+    ```html
+    <meta name="application-name" content="Name of Rails Application">
+    ```
+
+    *Steve Polito*
+
 *   Use `secret_key_base` from ENV or credentials when present locally.
 
     When ENV["SECRET_KEY_BASE"] or

railties/lib/rails/generators/rails/app/templates/app/views/layouts/application.html.erb.tt

@@ -4,6 +4,7 @@
     <title><%%= content_for(:title) || "<%= app_name.titleize %>" %></title>
     <meta name="viewport" content="width=device-width,initial-scale=1">
     <meta name="apple-mobile-web-app-capable" content="yes">
+    <meta name="application-name" content="<%= app_name.titleize %>">
     <meta name="mobile-web-app-capable" content="yes">
     <%%= csrf_meta_tags %>
     <%%= csp_meta_tag %>

railties/test/generators/app_generator_test.rb

@@ -443,6 +443,7 @@ def test_application_names_are_not_singularized
   def test_application_name_is_normalized_in_config
     run_generator [File.join(destination_root, "MyWebSite"), "-d", "postgresql"]
     assert_file "MyWebSite/app/views/layouts/application.html.erb", /content_for\(:title\) \|\| "My Web Site"/
+    assert_file "MyWebSite/app/views/layouts/application.html.erb", /meta\sname="application-name"\scontent="My Web Site/
     assert_file "MyWebSite/config/database.yml", /my_web_site_production/
   end