Add API method for updating a sticker in a guild.

lib/discordrb/api/server.rb

@@ -534,6 +534,21 @@ def add_sticker(token, server_id, file, name, description, tags, reason = nil)
     )
   end
 
+  # Changes a sticker's name, description, or tags.
+  # https://discord.com/developers/docs/resources/emoji#modify-guild-emoji
+  def edit_sticker(token, server_id, sticker_id, name, description, tags, reason = nil)
+    Discordrb::API.request(
+      :guilds_sid_stickers_eid,
+      server_id,
+      :patch,
+      "#{Discordrb::API.api_base}/guilds/#{server_id}/stickers/#{sticker_id}",
+      { name: name, description: description, tags: tags }.to_json,
+      Authorization: token,
+      content_type: :json,
+      'X-Audit-Log-Reason': reason
+    )
+  end
+
   # Available voice regions for this server
   # https://discord.com/developers/docs/resources/guild#get-guild-voice-regions
   def regions(token, server_id)