message: add message.channel
diff: @@ -30,6 +30,9 @@ import { Member } from "./member.ts";
  import { Role } from "./role.ts";
  const baseMessage: Partial<Message> = {
  + get channel() {
  + return cache.channels.get(this.channelID!);
  + },
  get guild() {
  if (!this.guildID) return;
  return cache.guilds.get(this.guildID);
  @@ -207,6 +210,8 @@ export interface Message {
  // GETTERS
  + /** The channel where this message was sent. Can be undefined if uncached. */
  + channel?: Channel;
  /** The guild of this message. Can be undefined if not in cache or in DM */
  guild?: Guild;
  /** The member for the user who sent the message. Can be undefined if not in cache or in dm. */
  