fix page style and format

404.html → 404.md

@@ -1,6 +1,5 @@
 ---
 permalink: /404.html
-layout: default
 ---
 
 <style type="text/css" media="screen">

Gemfile

@@ -1,22 +1,12 @@
 source "https://rubygems.org"
-# Hello! This is where you manage which Jekyll version is used to run.
-# When you want to use a different version, change it below, save the
-# file and run `bundle install`. Run Jekyll with `bundle exec`, like so:
-#
-#     bundle exec jekyll serve
-#
-# This will help ensure the proper Jekyll version is running.
-# Happy Jekylling!
-gem "jekyll", "~> 4.3.3"
-# This is the default theme for new Jekyll sites. You may change this to anything you like.
-gem "minima", "~> 2.5"
-# If you want to use GitHub Pages, remove the "gem "jekyll"" above and
-# uncomment the line below. To upgrade, run `bundle update github-pages`.
-# gem "github-pages", group: :jekyll_plugins
-# If you have any plugins, put them here!
+
+gem "jekyll"
+gem "github-pages", group: :jekyll_plugins
 group :jekyll_plugins do
   gem "jekyll-feed", "~> 0.12"
 end
+# Arch bug: https://www.adamsdesk.com/posts/jekyll-fix-cannot-load-such-file-json/
+gem "json"
 
 # Windows and JRuby does not include zoneinfo files, so bundle the tzinfo-data gem
 # and associated library.
@@ -32,5 +22,4 @@ gem "wdm", "~> 0.1.1", :platforms => [:mingw, :x64_mingw, :mswin]
 # do not have a Java counterpart.
 gem "http_parser.rb", "~> 0.6.0", :platforms => [:jruby]
 
-# gem "webrick", "~> 1.8"
-gem "webrick", ">= 0"
+gem "webrick", "~> 1.8"