message: feat(types): add attachments field to EditWebhookMessage
  Reference:
diff: import { Embed } from "../embeds/embed.ts";
  import { AllowedMentions } from "../messages/allowed_mentions.ts";
  -import { FileContent } from "../mod.ts";
  +import { FileContent } from "../misc/file_content.ts";
  +import { Attachment } from "../messages/attachment.ts";
  /** https://discord.com/developers/docs/resources/webhook#edit-webhook-message-jsonform-params */
  export interface EditWebhookMessage {
  @@ -12,4 +13,6 @@ export interface EditWebhookMessage {
  file: FileContent | FileContent[];
  /** Allowed mentions for the message */
  allowedMentions?: AllowedMentions | null;
  + /** Attached files to keep. */
  + attachments?: Attachment | null;
  }
  