message: Pass MIME type of custom emoji to be uploaded
  This ensures the media store on the Matrix side knows how to handle the emoji. Was able to use this change + to get animated discord emoji bridging nicely.
diff: @@ -574,7 +574,8 @@ export class DiscordBot {
  const url = `https://cdn.discordapp.com/emojis/${id}${animated ? ".gif" : ".png"}`;
  const intent = this.bridge.botIntent;
  const content = await Util.DownloadFile(url);
  - const mxcUrl = await this.bridge.botIntent.underlyingClient.uploadContent(content, undefined, name);
  + const type = animated ? "image/gif" : "iamge/png"
  + const mxcUrl = await this.bridge.botIntent.underlyingClient.uploadContent(content, type, name);
  dbEmoji.EmojiId = id;
  dbEmoji.Name = name;
  dbEmoji.Animated = animated;
  