Update support for Unicode 15.1

Upgrade to start using Unicode 15.1 emojis. Note that while 16.0 was just released, noto-emoji doesn't yet support it. Various things start breaking without the proper fallback images, and it's better to wait until 16 is a little more prevalent.

• load the Unicode emoji-test.txt file as the main basis for emoji data
• load the gemojione data, adding as aliases
• load any additional aliases

Closes #28 (closed)

lib/tanuki_emoji/db/additional_aliases.rb

+# frozen_string_literal: true
+
+require 'json'
+
+module TanukiEmoji
+  module Db
+    # Reads and adds aliases from additional_aliases.json
+    class AdditionalAliases
+      DATA_FILE = 'vendor/additional_aliases.json'
+
+      def self.data_file
+        File.expand_path(File.join(__dir__, '../../../', DATA_FILE))
+      end
+
+      attr_reader :data_file
+
+      def initialize(index:, data_file: self.class.data_file)
+        @data_file = data_file
+        @index = index
+      end
+
+      def load!
+        db = File.open(data_file, 'r:UTF-8') do |file|
+          JSON.parse(file.read, symbolize_names: true)
+        end
+
+        db.each do |_alpha_code, emoji_data|
+          emoji = @index.find_by_codepoints(emoji_data[:emoji])
+
+          next unless emoji
+
+          emoji_data[:aliases].each do |code|
+            emoji.add_alias(code)
+          end
+
+          emoji.noto_image = emoji_data[:noto_image] if emoji_data[:noto_image]
+
+          @index.update(emoji)
+        end
+      end
+    end
+  end
+end