Fix #4058: FontAwesome CDN is slow/blocking.

Switch to the free self-hosted version of FontAwesome. We're not using
any Pro icons, so the Pro version isn't necessary.

app/javascript/packs/application.js

@@ -25,6 +25,9 @@ require("jquery-ui/themes/base/draggable.css");
 require("jquery-ui/themes/base/resizable.css");
 require("jquery-ui/themes/base/theme.css");
 
+require("@fortawesome/fontawesome-free/css/all.css");
+require("@fortawesome/fontawesome-free/js/all.js");
+
 importAll(require.context('../src/javascripts', true, /\.js(\.erb)?$/));
 importAll(require.context('../src/styles', true, /\.s?css(?:\.erb)?$/));
 

app/views/layouts/blank.html.erb

@@ -8,7 +8,6 @@
   <%= auto_discovery_link_tag :atom, posts_path(:format => "atom", :tags => params[:tags]) %>
   <%= raw Danbooru.config.custom_html_header_content %>
   <script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.4.1/jquery.min.js"></script>
-  <link rel="stylesheet" href="https://use.fontawesome.com/releases/v5.3.1/css/all.css" integrity="sha384-mzrmE5qonljUremFsqc01SB46JvROS7bZs3IO2EmfFsd15uHvIt+Y8vEf7N7fWAU" crossorigin="anonymous">
   <%= javascript_pack_tag "application" %>
   <%= stylesheet_pack_tag "application" %>
   <%= yield :html_header %>

app/views/layouts/default.html.erb

@@ -68,12 +68,6 @@
     "url" : "<%= root_url %>"
   }
   </script>
-  <% if request.domain =~ /donmai\.us/ %>
-    <!-- this is only usable on danbooru.donmai.us -->
-    <link rel="stylesheet" href="https://pro.fontawesome.com/releases/v5.7.1/css/all.css" integrity="sha384-6jHF7Z3XI3fF4XZixAuSu0gGKrXwoX/w3uFPxC56OtjChio7wtTGJWRW53Nhx6Ev" crossorigin="anonymous">
-  <% else %>
-    <link rel="stylesheet" href="https://use.fontawesome.com/releases/v5.7.1/css/all.css" integrity="sha384-fnmOCqbTlWIlj8LyTjo7mOUStjsKC4pOpQbqyi7RrhN7udi9RwhKkMHpvLbHG9Sr" crossorigin="anonymous">
-<% end %>
   <script>
     if (typeof window.Danbooru !== "object") {
       window.Danbooru = {};