html: standardize font sizes and heading tags.

Standardize font sizes and heading tags (<h1>-<h6>) to be more
consistent across the site.

Changes:

* Introduce font size CSS variables and start replacing hardcoded font
  sizes with standard sizes.
* Change header tags to use only one <h1> per page. One <h1> per page is
  recommended for SEO purposes. Usually this is for the page title, like
  in forum threads or wiki pages.
* Standardize on <h2> for section headers in sidebars and <h3> for
  smaller subsection headers. Don't use <h4>-<h6>.
* In DText, make h1-h4 headers all the same size. Standard wiki style is
  to ignore h1-h3 and start at h4.
* In DText, make h4-h6 the same size as the h1-h3 tags outside of DText.
* In the tag list, change the <h1> and <h2> tag category headers to <h3>.
* Make usernames in comments and forum posts smaller. Also change the
  <h4> tag for the commenter name to <div class="author-name">.
* Make the tag list, paginator, and nav menu smaller on mobile.
* Change h1#app-name-header to a#app-name-header.

config/danbooru_default_config.rb

@@ -177,7 +177,6 @@ module Danbooru
           "category" => 0,
           "short" => "gen",
           "extra" => [],
-          "header" => %{<h1 class="general-tag-list">Tags</h1>},
           "relatedbutton" => "General",
           "css" => {
             "color" => "var(--general-tag-color)",
@@ -188,7 +187,6 @@ module Danbooru
           "category" => 4,
           "short" => "char",
           "extra" => ["ch"],
-          "header" => %{<h2 class="character-tag-list">Characters</h2>},
           "relatedbutton" => "Characters",
           "css" => {
             "color" => "var(--character-tag-color)",
@@ -199,7 +197,6 @@ module Danbooru
           "category" => 3,
           "short" => "copy",
           "extra" => ["co"],
-          "header" => %{<h2 class="copyright-tag-list">Copyrights</h2>},
           "relatedbutton" => "Copyrights",
           "css" => {
             "color" => "var(--copyright-tag-color)",
@@ -210,7 +207,6 @@ module Danbooru
           "category" => 1,
           "short" => "art",
           "extra" => [],
-          "header" => %{<h2 class="artist-tag-list">Artists</h2>},
           "relatedbutton" => "Artists",
           "css" => {
             "color" => "var(--artist-tag-color)",
@@ -221,7 +217,6 @@ module Danbooru
           "category" => 5,
           "short" => "meta",
           "extra" => [],
-          "header" => %{<h2 class="meta-tag-list">Meta</h2>},
           "relatedbutton" => nil,
           "css" => {
             "color" => "var(--meta-tag-color)",

config/initializers/inflections.rb

@@ -3,12 +3,13 @@
 # Add new inflection rules using the following format. Inflections
 # are locale specific, and you may define rules for as many different
 # locales as you wish. All of these examples are active by default:
-# ActiveSupport::Inflector.inflections(:en) do |inflect|
+ActiveSupport::Inflector.inflections(:en) do |inflect|
+  inflect.uncountable "general"
 #   inflect.plural /^(ox)$/i, '\1en'
 #   inflect.singular /^(ox)en/i, '\1'
 #   inflect.irregular 'person', 'people'
 #   inflect.uncountable %w( fish sheep )
-# end
+end
 
 # These inflection rules are supported but not enabled by default:
 # ActiveSupport::Inflector.inflections(:en) do |inflect|