Adds the ability to define a custom status for a bot

  Possible for some time apparently (https://discord.com/developers/docs/change-log#aug-8-2023)
  However, a bot can only define customizable text, no emoji can be defined
  + Adds a test/example file for custom status display

examples/custom_status.rb

@@ -0,0 +1,44 @@
+# frozen_string_literal: true
+
+require 'discordrb'
+
+bot = Discordrb::Bot.new token: ENV.fetch('DISCORDRB_TOKEN')
+custom_status = ['Hello World!', '❤️ Love you', 'Finally custom status 🎉']
+initialized = false
+thread = []
+
+bot.ready do |_|
+  next if initialized
+
+  bot.game = 'game'
+  sleep 5
+
+  bot.listening = 'music'
+  sleep 5
+
+  bot.watching = 'you'
+  sleep 5
+
+  bot.competing = 'mario kart'
+  sleep 5
+
+  bot.stream('discordrb', 'https://twitch.tv/shardlab')
+  sleep 5
+
+  initialized = true
+  thread << Thread.new do
+    loop do
+      bot.custom_status = custom_status.first
+      custom_status.rotate!
+
+      sleep 5
+    end
+  end
+end
+
+at_exit do
+  thread.each(&:exit)
+  bot.stop
+end
+
+bot.run

lib/discordrb/bot.rb

@@ -538,7 +538,7 @@ def parse_mention(mention, server = nil)
     # @param since [Integer] When this status was set.
     # @param afk [true, false] Whether the bot is AFK.
     # @param activity_type [Integer] The type of activity status to display.
-    #   Can be 0 (Playing), 1 (Streaming), 2 (Listening), 3 (Watching), or 5 (Competing).
+    #   Can be 0 (Playing), 1 (Streaming), 2 (Listening), 3 (Watching), 4 (Custom), or 5 (Competing).
     # @see Gateway#send_status_update
     def update_status(status, activity, url, since = 0, afk = false, activity_type = 0)
       gateway_check
@@ -548,7 +548,11 @@ def update_status(status, activity, url, since = 0, afk = false, activity_type =
       @streamurl = url
       type = url ? 1 : activity_type
 
-      activity_obj = activity || url ? { 'name' => activity, 'url' => url, 'type' => type } : nil
+      activity_obj = if activity_type == 4
+                       { 'name' => activity, 'type' => type, 'state' => activity }
+                     else
+                       activity || url ? { 'name' => activity, 'url' => url, 'type' => type } : nil
+                     end
       @gateway.send_status_update(status, since, activity_obj, afk)
 
       # Update the status in the cache
@@ -599,6 +603,14 @@ def competing=(name)
       update_status(@status, name, nil, nil, nil, 5)
     end
 
+    # Sets the currently custom status to the specified name.
+    # @param name [String] The custom status.
+    # @return [String] The custom status that is being used now.
+    def custom_status=(name)
+      gateway_check
+      update_status(@status, name, nil, nil, nil, 4)
+    end
+
     # Sets status to online.
     def online
       gateway_check