Doc fixes, mostly pertaining to Snowflakes (#1218)

GUS!!!! @GusCaplan

src/client/Client.js

@@ -210,7 +210,7 @@ class Client extends EventEmitter {
 
   /**
    * All active voice connections that have been established, mapped by channel ID
-   * @type {Collection<string, VoiceConnection>}
+   * @type {Collection<Snowflake, VoiceConnection>}
    * @readonly
    */
   get voiceConnections() {
@@ -303,7 +303,7 @@ class Client extends EventEmitter {
   /**
    * Obtains a user from Discord, or the user cache if it's already available.
    * <warn>This is only available when using a bot account.</warn>
-   * @param {string} id ID of the user
+   * @param {Snowflake} id ID of the user
    * @param {boolean} [cache=true] Whether to cache the new user object if it isn't already
    * @returns {Promise<User>}
    */
@@ -324,7 +324,7 @@ class Client extends EventEmitter {
 
   /**
    * Obtains a webhook from Discord.
-   * @param {string} id ID of the webhook
+   * @param {Snowflake} id ID of the webhook
    * @param {string} [token] Token for the webhook
    * @returns {Promise<Webhook>}
    */
@@ -467,7 +467,7 @@ class Client extends EventEmitter {
 
   /**
    * Adds/updates a friend's presence in {@link Client#presences}.
-   * @param {string} id ID of the user
+   * @param {Snowflake} id ID of the user
    * @param {Object} presence Raw presence object from Discord
    * @private
    */